Substate

A lightweight, type-safe state management library that combines the Pub/Sub pattern with immutable state management.

Substate provides a simple yet powerful way to manage application state with built-in event handling, middleware support, and seamless synchronization capabilities. Perfect for applications that need reactive state management without the complexity of larger frameworks.

📑 Table of Contents

• 📦 Installation
• ✨ Features
• 🚀 Quick Start
• 🏷️ Tagged States
• 📚 Usage Examples
• 🎯 Framework Integrations
• 🔗 Sync - Unidirectional Data Binding
• 📖 API Reference
• 🧠 Memory Management
• ⚡ Performance Benchmarks
• 🏁 Performance Comparison Benchmarks
• 🔄 Why Choose Substate?
• 📋 TypeScript Definitions
• 📈 Migration Guide
• 🔧 Troubleshooting
• 🛠️ Development
• 🤝 Contributing
• 📄 License

✨ Features

🚀 Lightweight - Tiny bundle size at ~11KB

Substate is designed to be minimal yet powerful. The core library weighs just ~11KB minified, making it perfect for applications where bundle size matters.

import { createStore } from 'substate'; // Only ~11KB total

🔒 Type-safe - Full TypeScript support with comprehensive type definitions

Complete TypeScript support with advanced type inference, ensuring type safety throughout your application.

interface User {
  id: number;
  name: string;
  email: string;
}

const userStore = createStore<User>({
  name: 'UserStore',
  state: { user: null as User | null, loading: false }
});

// TypeScript knows the exact shape of your state
userStore.updateState({ user: { id: 1, name: 'John', email: '[email protected]' } });

🔄 Reactive - Built-in Pub/Sub pattern for reactive state updates

Event-driven architecture with built-in subscription system for reactive updates.

const store = createStore({
  name: 'ReactiveStore',
  state: { count: 0 }
});

// Subscribe to state changes
store.on('UPDATE_STATE', (newState) => {
  console.log('State updated:', newState);
  // React to changes automatically
});

🕰️ Time Travel - Complete state history with ability to navigate between states

Full state history with configurable memory management. Navigate through state changes like a debugger.

const store = createStore({
  name: 'TimeTravelStore',
  state: { count: 0 }
});

// Make some changes
store.updateState({ count: 1 });
store.updateState({ count: 2 });
store.updateState({ count: 3 });

// Go back in time
console.log(store.getState(0)); // { count: 0 } - initial state
console.log(store.getState(1)); // { count: 1 } - first update
console.log(store.getState(2)); // { count: 2 } - second update

🏷️ Tagged States - Named checkpoints for easy state restoration

Create named checkpoints in your state history for easy navigation and debugging.

const gameStore = createStore({
  name: 'GameStore',
  state: { level: 1, score: 0 }
});

// Create a checkpoint
gameStore.updateState({ level: 5, score: 1250, $tag: 'level-5-start' });

// Later, jump back to that checkpoint
gameStore.jumpToTag('level-5-start');
console.log(gameStore.getCurrentState()); // { level: 5, score: 1250 }

🎯 Immutable - Automatic deep cloning prevents accidental state mutations

Automatic deep cloning ensures immutability by default, preventing accidental mutations.

const store = createStore({
  name: 'ImmutableStore',
  state: { user: { name: 'John', settings: { theme: 'dark' } } }
});

// State is automatically deep cloned - original object is safe
const originalState = store.getCurrentState();
originalState.user.name = 'Jane'; // This won't affect the store

console.log(store.getProp('user.name')); // Still 'John'

🔗 Sync - Unidirectional data binding with middleware transformations

Connect your store to UI components or external systems with powerful sync capabilities.

const store = createStore({
  name: 'SyncStore',
  state: { price: 29.99 }
});

// Sync to UI with formatting
const uiModel = { formattedPrice: '' };
const unsync = store.sync({
  readerObj: uiModel,
  stateField: 'price',
  readField: 'formattedPrice',
  beforeUpdate: [(price) => `$${price.toFixed(2)}`]
});

console.log(uiModel.formattedPrice); // '$29.99'

🎪 Middleware - Extensible with before/after update hooks

Powerful middleware system for logging, validation, persistence, and custom logic.

const store = createStore({
  name: 'MiddlewareStore',
  state: { count: 0 },
  beforeUpdate: [
    (store, action) => {
      console.log('About to update:', action);
      // Validation logic here
    }
  ],
  afterUpdate: [
    (store, action) => {
      console.log('Updated to:', store.getCurrentState());
      // Persistence logic here
    }
  ]
});

🌳 Nested Props - Easy access to nested properties with optional dot notation or standard object spread

Flexible nested property access with both dot notation convenience and object spread patterns.

const store = createStore({
  name: 'NestedStore',
  state: {
    user: {
      profile: { name: 'John', email: '[email protected]' }
    }
  }
});

// Dot notation (convenient)
store.updateState({ 'user.profile.name': 'Jane' });

// Object spread (explicit)
store.updateState({
  user: {
    ...store.getProp('user'),
    profile: {
      ...store.getProp('user.profile'),
      name: 'Jane'
    }
  }
});

// Both approaches work equally well

📦 Framework Agnostic - Works with any JavaScript framework or vanilla JS

No framework dependencies - use with React, Vue, Angular, Svelte, or vanilla JavaScript.

// Vanilla JavaScript
const store = createStore({ name: 'VanillaStore', state: { count: 0 } });

// React
import { useEffect, useState } from 'react';
function Counter() {
  const [count, setCount] = useState(0);
  useEffect(() => {
    store.on('UPDATE_STATE', (state) => setCount(state.count));
  }, []);
}

// Vue, Angular, Svelte - works with all frameworks!

📦 Installation

npm

npm install substate

yarn

yarn add substate

pnpm

pnpm add substate

Requirements

• Node.js: >= 16.0.0
• TypeScript: >= 4.5.0 (for TypeScript support)
• Peer Dependencies: clone-deep, object-bystring

Bundle Size

• Minified: ~11KB
• Gzipped: ~4KB

CDN

<!-- UMD Build -->
<script src="https://cdn.jsdelivr.net/npm/substate@latest/dist/index.umd.js"></script>

<!-- ESM Build -->
<script type="module">
  import { createStore } from 'https://cdn.jsdelivr.net/npm/substate@latest/dist/index.esm.js';
</script>

🚀 Quick Start

Installation & Basic Usage

npm install substate

import { createStore } from 'substate';

// Create a simple counter store
const counterStore = createStore({
  name: 'CounterStore',
  state: { count: 0, lastUpdated: Date.now() }
});

// Update state
counterStore.updateState({ count: 1 });
console.log(counterStore.getCurrentState()); // { count: 1, lastUpdated: 1234567890 }

// Listen to changes
counterStore.on('UPDATE_STATE', (newState) => {
  console.log('Counter updated:', newState.count);
});

Next Steps

1. 📚 Usage Examples - Learn through practical examples
2. 🔗 Sync - Unidirectional Data Binding - Connect your store to UI components
3. 🏷️ Tagged States - Save and restore state checkpoints
4. 📖 API Reference - Complete method documentation

Common Patterns

Counter with Actions

const counterStore = createStore({
  name: 'Counter',
  state: { count: 0 }
});

// Action functions (optional but recommended)
function increment() {
  counterStore.updateState({
    count: counterStore.getProp('count') + 1
  });
}

function decrement() {
  counterStore.updateState({
    count: counterStore.getProp('count') - 1
  });
}

function reset() {
  counterStore.resetState(); // Back to initial state
}

// Subscribe to changes
counterStore.on('UPDATE_STATE', (state) => {
  console.log('Count changed to:', state.count);
});

// Use the actions
increment(); // count: 1
increment(); // count: 2
decrement(); // count: 1
reset();     // count: 0

Form State Management

const formStore = createStore({
  name: 'ContactForm',
  state: {
    name: '',
    email: '',
    message: '',
    isSubmitting: false,
    errors: {}
  }
});

// Update form fields
function updateField(field: string, value: string) {
  formStore.updateState({ [field]: value });
}

// Submit form
async function submitForm() {
  formStore.updateState({ isSubmitting: true, errors: {} });

  try {
    await submitToAPI(formStore.getCurrentState());
    console.log('Form submitted successfully!');
    formStore.resetState(); // Clear form
  } catch (error) {
    formStore.updateState({
      isSubmitting: false,
      errors: { submit: error.message }
    });
  }
}

// Listen for form changes
formStore.on('UPDATE_STATE', (state) => {
  if (state.isSubmitting) {
    console.log('Submitting form...');
  }
});

🏷️ Tagged States

Named State Checkpoint System

Tagged states is a Named State Checkpoint System that allows you to create semantic, named checkpoints in your application's state history. Instead of navigating by numeric indices, you can jump to meaningful moments in your app's lifecycle.

What is a Named State Checkpoint System?

A Named State Checkpoint System provides:

• Semantic Navigation: Jump to states by meaningful names instead of numbers
• State Restoration: Restore to any named checkpoint and continue from there
• Debugging Support: Tag known-good states for easy rollback
• User Experience: Enable features like "save points" and "undo to specific moment"

Basic Usage

import { createStore } from 'substate';

const gameStore = createStore({
  name: 'GameStore',
  state: { level: 1, score: 0, lives: 3 }
});

// Create tagged checkpoints with meaningful names
gameStore.updateState({ 
  level: 5, 
  score: 1250, 
  $tag: "level-5-start" 
});

gameStore.updateState({ 
  level: 10, 
  score: 5000, 
  lives: 2, 
  $tag: "boss-fight" 
});

// Jump back to any tagged state by name
gameStore.jumpToTag("level-5-start");
console.log(gameStore.getCurrentState()); // { level: 5, score: 1250, lives: 3 }

// Access tagged states without changing current state
const bossState = gameStore.getTaggedState("boss-fight");
console.log(bossState); // { level: 10, score: 5000, lives: 2 }

// Manage your tags
console.log(gameStore.getAvailableTags()); // ["level-5-start", "boss-fight"]
gameStore.removeTag("level-5-start");

Advanced Checkpoint Patterns

Form Wizard with Step Restoration

const formStore = createStore({
  name: 'FormWizard',
  state: {
    currentStep: 1,
    personalInfo: { firstName: '', lastName: '', email: '' },
    addressInfo: { street: '', city: '', zip: '' },
    paymentInfo: { cardNumber: '', expiry: '' }
  }
});

// Save progress at each completed step
function completePersonalInfo(data) {
  formStore.updateState({
    personalInfo: data,
    currentStep: 2,
    $tag: "step-1-complete"
  });
}

function completeAddressInfo(data) {
  formStore.updateState({
    addressInfo: data,
    currentStep: 3,
    $tag: "step-2-complete"
  });
}

// User can jump back to any completed step
function goToStep(stepNumber) {
  const stepTag = `step-${stepNumber}-complete`;
  if (formStore.getAvailableTags().includes(stepTag)) {
    formStore.jumpToTag(stepTag);
  }
}

// Usage
goToStep(1); // Jump back to personal info step
goToStep(2); // Jump back to address info step

Debugging and Error Recovery

const appStore = createStore({
  name: 'AppStore',
  state: {
    userData: null,
    settings: {},
    lastError: null
  }
});

// Tag known good states for debugging
function markKnownGoodState() {
  appStore.updateState({
    $tag: "last-known-good"
  });
}

// When errors occur, jump back to known good state
function handleError(error) {
  console.error('Error occurred:', error);
  
  if (appStore.getAvailableTags().includes("last-known-good")) {
    console.log('Rolling back to last known good state...');
    appStore.jumpToTag("last-known-good");
  }
}

// Tag states before risky operations
function performRiskyOperation() {
  appStore.updateState({
    $tag: "before-risky-operation"
  });
  
  // ... perform operation that might fail
  
  if (operationFailed) {
    appStore.jumpToTag("before-risky-operation");
  }
}

Game Save System

const gameStore = createStore({
  name: 'GameStore',
  state: {
    player: { health: 100, level: 1, inventory: [] },
    world: { currentArea: 'town', discoveredAreas: [] },
    quests: { active: [], completed: [] }
  }
});

// Auto-save system
function autoSave() {
  const timestamp = new Date().toISOString();
  gameStore.updateState({
    $tag: `auto-save-${timestamp}`
  });
}

// Manual save system
function manualSave(saveName) {
  gameStore.updateState({
    $tag: `save-${saveName}`
  });
}

// Load save system
function loadSave(saveName) {
  const saveTag = `save-${saveName}`;
  if (gameStore.getAvailableTags().includes(saveTag)) {
    gameStore.jumpToTag(saveTag);
    return true;
  }
  return false;
}

// Get all available saves
function getAvailableSaves() {
  return gameStore.getAvailableTags()
    .filter(tag => tag.startsWith('save-'))
    .map(tag => tag.replace('save-', ''));
}

// Usage
manualSave("checkpoint-1");
manualSave("before-boss-fight");
loadSave("checkpoint-1");

Feature Flag and A/B Testing

const experimentStore = createStore({
  name: 'ExperimentStore',
  state: {
    features: {},
    userGroup: null,
    experimentResults: {}
  }
});

// Tag different experiment variants
function setupExperimentVariant(variant) {
  experimentStore.updateState({
    userGroup: variant,
    $tag: `experiment-${variant}`
  });
}

// Jump between experiment variants
function switchToVariant(variant) {
  const variantTag = `experiment-${variant}`;
  if (experimentStore.getAvailableTags().includes(variantTag)) {
    experimentStore.jumpToTag(variantTag);
  }
}

// Usage
setupExperimentVariant("control");
setupExperimentVariant("variant-a");
setupExperimentVariant("variant-b");

switchToVariant("variant-a"); // Switch to variant A

🎯 Common Tagging Patterns

// Form checkpoints
formStore.updateState({ ...formData, $tag: "before-validation" });

// API operation snapshots  
store.updateState({ users: userData, $tag: "after-user-import" });

// Feature flags / A-B testing
store.updateState({ features: newFeatures, $tag: "experiment-variant-a" });

// Debugging checkpoints
store.updateState({ debugInfo: data, $tag: "issue-reproduction" });

// Game saves
gameStore.updateState({ saveData, $tag: `save-${Date.now()}` });

// Workflow states
workflowStore.updateState({ status: "approved", $tag: "workflow-approved" });

// User session states
sessionStore.updateState({ user: userData, $tag: "user-logged-in" });

📚 Usage Examples

1. Todo List Management

import { createStore } from 'substate';

interface Todo {
  id: string;
  text: string;
  completed: boolean;
}

const todoStore = createStore({
  name: 'TodoStore',
  state: {
    todos: [] as Todo[],
    filter: 'all' as 'all' | 'active' | 'completed'
  },
  defaultDeep: true
});

// Add a new todo
function addTodo(text: string) {
  const currentTodos = todoStore.getProp('todos') as Todo[];
  todoStore.updateState({
    todos: [...currentTodos, {
      id: crypto.randomUUID(),
      text,
      completed: false
    }]
  });
}

// Toggle todo completion
function toggleTodo(id: string) {
  const todos = todoStore.getProp('todos') as Todo[];
  todoStore.updateState({
    todos: todos.map(todo => 
      todo.id === id ? { ...todo, completed: !todo.completed } : todo
    )
  });
}

// Subscribe to changes
todoStore.on('UPDATE_STATE', (state) => {
  console.log(`${state.todos.length} todos, filter: ${state.filter}`);
});

2. User Authentication Store

import { createStore } from 'substate';

const authStore = createStore({
  name: 'AuthStore',
  state: {
    user: null,
    isAuthenticated: false,
    loading: false,
    error: null
  },
  beforeUpdate: [
    (store, action) => {
      // Log all state changes
      console.log('Auth state changing:', action);
    }
  ],
  afterUpdate: [
    (store, action) => {
      // Persist authentication state
      if (action.user || action.isAuthenticated !== undefined) {
        localStorage.setItem('auth', JSON.stringify(store.getCurrentState()));
      }
    }
  ]
});

// Login action
async function login(email: string, password: string) {
  authStore.updateState({ loading: true, error: null });
  
  try {
    const user = await authenticateUser(email, password);
    authStore.updateState({
      user,
      isAuthenticated: true,
      loading: false
    });
  } catch (error) {
    authStore.updateState({
      error: error.message,
      loading: false,
      isAuthenticated: false
    });
  }
}

3. Shopping Cart with Middleware

import { createStore } from 'substate';

const cartStore = createStore({
  name: 'CartStore',
  state: {
    items: [],
    total: 0,
    tax: 0,
    discount: 0
  },
  defaultDeep: true,
  afterUpdate: [
    // Automatically calculate totals after any update
    (store) => {
      const state = store.getCurrentState();
      const subtotal = state.items.reduce((sum, item) => sum + (item.price * item.quantity), 0);
      const tax = subtotal * 0.08; // 8% tax
      const total = subtotal + tax - state.discount;
      
      // Update calculated fields without triggering infinite loop
      store.stateStorage[store.currentState] = {
        ...state,
        total,
        tax
      };
    }
  ]
});

function addToCart(product) {
  const items = cartStore.getProp('items');
  const existingItem = items.find(item => item.id === product.id);
  
  if (existingItem) {
    cartStore.updateState({
      items: items.map(item =>
        item.id === product.id
          ? { ...item, quantity: item.quantity + 1 }
          : item
      )
    });
  } else {
    cartStore.updateState({
      items: [...items, { ...product, quantity: 1 }]
    });
  }
}

4. Working with Nested Properties

const userStore = createStore({
  name: 'UserStore',
  state: {
    profile: {
      personal: {
        name: 'John Doe',
        email: '[email protected]'
      },
      preferences: {
        theme: 'dark',
        notifications: true
      }
    },
    settings: {
      privacy: {
        publicProfile: false
      }
    }
  },
  defaultDeep: true
});

// Update nested properties using dot notation (convenient for simple updates)
userStore.updateState({ 'profile.personal.name': 'Jane Doe' });
userStore.updateState({ 'profile.preferences.theme': 'light' });
userStore.updateState({ 'settings.privacy.publicProfile': true });

// Or update nested properties using object spread (no string notation required)
userStore.updateState({ 
  profile: { 
    ...userStore.getProp('profile'),
    personal: { 
      ...userStore.getProp('profile.personal'),
      name: 'Jane Doe' 
    }
  }
});

// Both approaches work - choose what feels more natural for your use case
userStore.updateState({ 'profile.preferences.theme': 'light' }); // Dot notation
userStore.updateState({ 
  profile: { 
    ...userStore.getProp('profile'),
    preferences: { 
      ...userStore.getProp('profile.preferences'),
      theme: 'light' 
    }
  }
}); // Object spread

// Get nested properties
console.log(userStore.getProp('profile.personal.name')); // 'Jane Doe'
console.log(userStore.getProp('profile.preferences')); // { theme: 'light', notifications: true }

🎯 Framework Integrations

React/Preact

import { createStore, type TState } from "substate";
import { useSubstate, useSubstateActions } from "substate/react"; // or "substate/preact"

type MyAppState = TState & {
  firstName: string;
}

const store = createStore<MyAppState>({
  state: {
    firstName: "Ralph"
  }
});

function MyApp(){
  const { state } = useSubstate(store (state) => state); //whole state
  const { firstName } = useSubstate(store, (state) => state.firstName); //state with seletor

const { 
    updateState, 
    resetState, 
    jumpToTag, 
    getAvailableTags,
    getMemoryUsage 
  } = useSubstateActions(store);
  return (
    <input onChange={e => updateState({firstName: e.target.value})} value={firstName}/>
  );
}

Lit

import { LitElement, html } from 'lit'
import { customElement, property } from 'lit/decorators.js'
import { store } from '../../store'; // store instance

@customElement('counter')
export class Counter LitElement {

  private syncedCount;

  constructor() {
    super();
    this.syncedCount = store.sync({
      readerObj: this as Multiplier,
      stateField: 'count',
    });
  }

  disconnectedCallback() {
    super.disconnectedCallback();
    this.syncedCount.unsync();
  }

  @property({ type: Number })
  count = 0;

  render() {
    return html`
    <div>
       ${this.count}
       <button type="button" @click=${this._increment}
        +1
       </button>
    </div>
    `
  }

  private _increment(){
    store.updateState({
      count: this.count + 1
    });
  }
}

declare global {
  interface HTMLElementTagNameMap {
    'multiplier-el': Multiplier
  }
}

```## 🔗 Sync - Unidirectional Data Binding

One of Substate's most powerful features is the `sync` method, which provides unidirectional data binding between your store and any target object (like UI models, form objects, or API payloads).

### Basic Sync Example

```typescript
import { createStore } from 'substate';

const userStore = createStore({
  name: 'UserStore',
  state: { userName: 'John', age: 25 }
});

// Target object (could be a UI model, form, etc.)
const uiModel = { displayName: '', userAge: 0 };

// Sync userName from store to displayName in uiModel
const unsync = userStore.sync({
  readerObj: uiModel,
  stateField: 'userName',
  readField: 'displayName'
});

console.log(uiModel.displayName); // 'John' - immediately synced

// When store updates, uiModel automatically updates
userStore.updateState({ userName: 'Alice' });
console.log(uiModel.displayName); // 'Alice'

// Changes to uiModel don't affect the store (unidirectional)
uiModel.displayName = 'Bob';
console.log(userStore.getProp('userName')); // Still 'Alice'

// Cleanup when no longer needed
unsync();

Sync with Middleware Transformations

const productStore = createStore({
  name: 'ProductStore',
  state: { 
    price: 29.99,
    currency: 'USD',
    name: 'awesome widget'
  }
});

const displayModel = { formattedPrice: '', productTitle: '' };

// Sync with transformation middleware
const unsyncPrice = productStore.sync({
  readerObj: displayModel,
  stateField: 'price',
  readField: 'formattedPrice',
  beforeUpdate: [
    // Transform price to currency format
    (price, context) => `$${price.toFixed(2)}`,
    // Add currency symbol based on store state
    (formattedPrice, context) => {
      const currency = productStore.getProp('currency');
      return currency === 'EUR' ? formattedPrice.replace('$', '€') : formattedPrice;
    }
  ],
  afterUpdate: [
    // Log the transformation
    (finalValue, context) => {
      console.log(`Price synced: ${finalValue} for field ${context.readField}`);
    }
  ]
});

const unsyncName = productStore.sync({
  readerObj: displayModel,
  stateField: 'name',
  readField: 'productTitle',
  beforeUpdate: [
    // Transform to title case
    (name) => name.split(' ').map(word =>
      word.charAt(0).toUpperCase() + word.slice(1)
    ).join(' ')
  ]
});

console.log(displayModel.formattedPrice); // '$29.99'
console.log(displayModel.productTitle); // 'Awesome Widget'

// Update triggers all synced transformations
productStore.updateState({ price: 39.99, name: 'super awesome widget' });
console.log(displayModel.formattedPrice); // '$39.99'
console.log(displayModel.productTitle); // 'Super Awesome Widget'

Real-world Sync Example: Form Binding

// Form state store
const formStore = createStore({
  name: 'FormStore',
  state: {
    user: {
      firstName: '',
      lastName: '',
      email: '',
      birthDate: null
    },
    validation: {
      isValid: false,
      errors: []
    }
  }
});

// Form UI object (could be from any UI framework)
const formUI = {
  fullName: '',
  emailInput: '',
  ageDisplay: '',
  submitEnabled: false
};

// Sync full name (combining first + last)
const unsyncName = formStore.sync({
  readerObj: formUI,
  stateField: 'user',
  readField: 'fullName',
  beforeUpdate: [
    (user) => `${user.firstName} ${user.lastName}`.trim()
  ]
});

// Sync email directly
const unsyncEmail = formStore.sync({
  readerObj: formUI,
  stateField: 'user.email',
  readField: 'emailInput'
});

// Sync age calculation from birth date
const unsyncAge = formStore.sync({
  readerObj: formUI,
  stateField: 'user.birthDate',
  readField: 'ageDisplay',
  beforeUpdate: [
    (birthDate) => {
      if (!birthDate) return 'Not provided';
      const age = new Date().getFullYear() - new Date(birthDate).getFullYear();
      return `${age} years old`;
    }
  ]
});

// Sync form validity to submit button
const unsyncValid = formStore.sync({
  readerObj: formUI,
  stateField: 'validation.isValid',
  readField: 'submitEnabled'
});

// Update form data
formStore.updateState({
  'user.firstName': 'John',
  'user.lastName': 'Doe',
  'user.email': '[email protected]',
  'user.birthDate': '1990-05-15',
  'validation.isValid': true
});

console.log(formUI);
// {
//   fullName: 'John Doe',
//   emailInput: '[email protected]', 
//   ageDisplay: '34 years old',
//   submitEnabled: true
// }

Multiple Sync Instances

You can sync the same state field to multiple targets with different transformations:

const dataStore = createStore({
  name: 'DataStore',
  state: { timestamp: Date.now() }
});

const dashboard = { lastUpdate: '' };
const report = { generatedAt: '' };
const api = { timestamp: 0 };

// Sync to dashboard with human-readable format
const unsync1 = dataStore.sync({
  readerObj: dashboard,
  stateField: 'timestamp',
  readField: 'lastUpdate',
  beforeUpdate: [(ts) => new Date(ts).toLocaleString()]
});

// Sync to report with ISO string
const unsync2 = dataStore.sync({
  readerObj: report,
  stateField: 'timestamp', 
  readField: 'generatedAt',
  beforeUpdate: [(ts) => new Date(ts).toISOString()]
});

// Sync to API with raw timestamp
const unsync3 = dataStore.sync({
  readerObj: api,
  stateField: 'timestamp' // uses same field name when readField omitted
});

// One update triggers all syncs
dataStore.updateState({ timestamp: Date.now() });

TypeScript Support

import { createStore, type ISubstate, type ICreateStoreConfig } from 'substate';

const config: ICreateStoreConfig = {
  name: 'TypedStore',
  state: { count: 0 },
  defaultDeep: true
};

const store: ISubstate = createStore(config);

📖 API Reference

createStore(config)

Factory function to create a new Substate store with a clean, intuitive API.

function createStore(config: ICreateStoreConfig): ISubstate

Parameters:

| Property | Type | Required | Default | Description | |----------|------|----------|---------|-------------| | name | string | ❌ | - | Unique identifier for the store | | state | object | ❌ | {} | Initial state object | | defaultDeep | boolean | ❌ | false | Enable deep cloning by default for all updates | | beforeUpdate | UpdateMiddleware[] | ❌ | [] | Functions called before each state update | | afterUpdate | UpdateMiddleware[] | ❌ | [] | Functions called after each state update | | maxHistorySize | number | ❌ | 50 | Maximum number of states to keep in history |

Returns: A new ISubstate instance

Example:

const store = createStore({
  name: 'MyStore',
  state: { count: 0 },
  defaultDeep: true,
  maxHistorySize: 25, // Keep only last 25 states for memory efficiency
  beforeUpdate: [(store, action) => console.log('Updating...', action)],
  afterUpdate: [(store, action) => console.log('Updated!', store.getCurrentState())]
});

Store Methods

updateState(action: IState): void

Updates the current state with new values. Supports both shallow and deep merging.

// Simple update
store.updateState({ count: 5 });

// Nested property update with dot notation (optional convenience feature)
store.updateState({ 'user.profile.name': 'John' });

// Or update nested properties using standard object spread (no strings required)
store.updateState({ 
  user: { 
    ...store.getProp('user'),
    profile: { 
      ...store.getProp('user.profile'),
      name: 'John' 
    }
  }
});

// Force deep cloning for this update
store.updateState({ 
  data: complexObject,
  $deep: true 
});

// Update with custom type identifier
store.updateState({ 
  items: newItems,
  $type: 'BULK_UPDATE'
});

// Adding a tag
store.updateState({
  items: importantItem,
  $tag: 'important-item-added'
});

Parameters:

• action - Object containing the properties to update
• action.$deep (optional) - Force deep cloning for this update
• action.$type (optional) - Custom identifier for this update
• action.$tag (optional) - Tag name to create a named checkpoint of this state

batchUpdateState(actions: Array<Partial<TSubstateState> & IState>): void

Updates multiple properties at once for better performance. This method is optimized for bulk operations and provides significant performance improvements over multiple individual updateState() calls.

// Instead of multiple individual updates (slower)
store.updateState({ counter: 1 });
store.updateState({ user: { name: "John" } });
store.updateState({ theme: "dark" });

// Use batch update for better performance
store.batchUpdateState([
  { counter: 1 },
  { user: { name: "John" } },
  { theme: "dark" }
]);

// Batch updates with complex operations
store.batchUpdateState([
  { 'user.profile.name': 'Jane' },
  { 'user.profile.email': '[email protected]' },
  { 'settings.theme': 'light' },
  { 'settings.notifications': true }
]);

// Batch updates with metadata
store.batchUpdateState([
  { data: newData, $type: 'DATA_IMPORT' },
  { lastUpdated: Date.now() },
  { version: '2.0.0' }
]);

Performance Benefits:

• Single state clone instead of multiple clones
• One event emission instead of multiple events
• Reduced middleware calls (if using middleware)
• Better memory efficiency

When to Use:

• Multiple related updates that should happen together
• Performance-critical code with frequent state changes
• Bulk operations like form submissions or data imports
• Reducing re-renders in React/Preact components

Parameters:

• actions - Array of update action objects (same format as updateState)

Smart Optimization: The method automatically detects if it can use the fast path (no middleware, no deep cloning, no tagging) and processes all updates in a single optimized operation. If any action requires the full feature set, it falls back to processing each action individually.

Example Use Cases:

// Form submission with multiple fields
function submitForm(formData) {
  store.batchUpdateState([
    { 'form.isSubmitting': true },
    { 'form.data': formData },
    { 'form.errors': [] },
    { 'form.lastSubmitted': Date.now() }
  ]);
}

// Bulk data import
function importData(items) {
  store.batchUpdateState([
    { 'data.items': items },
    { 'data.totalCount': items.length },
    { 'data.lastImport': Date.now() },
    { 'ui.showImportSuccess': true }
  ]);
}

// User profile update
function updateProfile(profileData) {
  store.batchUpdateState([
    { 'user.profile': profileData },
    { 'user.lastUpdated': Date.now() },
    { 'ui.profileUpdated': true }
  ]);
}

getCurrentState(): IState

Returns the current active state object.

const currentState = store.getCurrentState();
console.log(currentState); // { count: 5, user: { name: 'John' } }

getProp(prop: string): unknown

Retrieves a specific property from the current state using dot notation for nested access.

// Get top-level property
const count = store.getProp('count'); // 5

// Get nested property
const userName = store.getProp('user.profile.name'); // 'John'

// Get array element
const firstItem = store.getProp('items.0.title');

// Returns undefined for non-existent properties
const missing = store.getProp('nonexistent.path'); // undefined

getState(index: number): IState

Returns a specific state from the store's history by index.

// Get initial state (always at index 0)
const initialState = store.getState(0);

// Get previous state
const previousState = store.getState(store.currentState - 1);

// Get specific historical state
const specificState = store.getState(3);

resetState(): void

Resets the store to its initial state (index 0) and emits an UPDATE_STATE event.

store.resetState();
console.log(store.currentState); // 0
console.log(store.getCurrentState()); // Returns initial state

sync(config: ISyncConfig): () => void

Creates unidirectional data binding between a state property and a target object.

const unsync = store.sync({
  readerObj: targetObject,
  stateField: 'user.name',
  readField: 'displayName',
  beforeUpdate: [(value) => value.toUpperCase()],
  afterUpdate: [(value) => console.log('Synced:', value)]
});

// Call to cleanup the sync
unsync();

Parameters:

| Property | Type | Required | Description | |----------|------|----------|-------------| | readerObj | Record<string, unknown> | ✅ | Target object to sync to | | stateField | string | ✅ | State property to watch (supports dot notation) | | readField | string | ❌ | Target property name (defaults to stateField) | | beforeUpdate | BeforeMiddleware[] | ❌ | Transform functions applied before sync | | afterUpdate | AfterMiddleware[] | ❌ | Side-effect functions called after sync |

Returns: Function to call for cleanup (removes event listeners)

clearHistory(): void

Clears all state history except the current state to free up memory.

// After many state updates...
console.log(store.stateStorage.length); // 50+ states

store.clearHistory();
console.log(store.stateStorage.length); // 1 state
console.log(store.currentState); // 0

// Current state is preserved
console.log(store.getCurrentState()); // Latest state data

Use cases:

• Memory optimization in long-running applications
• Cleaning up after bulk operations
• Preparing for application state snapshots

limitHistory(maxSize: number): void

Sets a new limit for state history size and trims existing history if necessary.

// Current setup
store.limitHistory(10); // Keep only last 10 states

// If current history exceeds the limit, it gets trimmed
console.log(store.stateStorage.length); // Max 10 states

// Dynamic adjustment for debugging
if (debugMode) {
  store.limitHistory(100); // More history for debugging
} else {
  store.limitHistory(5);   // Minimal history for production
}

Parameters:

• maxSize - Maximum number of states to keep (minimum: 1)

Throws: Error if maxSize is less than 1

getMemoryUsage(): { stateCount: number; taggedCount: number; estimatedSizeKB: number }

Returns estimated memory usage information for performance monitoring.

const usage = store.getMemoryUsage();
console.log(`States: ${usage.stateCount}`);
console.log(`Estimated Size: ${usage.estimatedSizeKB}KB`);

// Memory monitoring
if (usage.estimatedSizeKB > 1000) {
  console.warn('Store using over 1MB of memory');
  store.clearHistory(); // Clean up if needed
}

// Performance tracking
setInterval(() => {
  const { stateCount, estimatedSizeKB } = store.getMemoryUsage();
  console.log(`Memory: ${estimatedSizeKB}KB (${stateCount} states)`);
}, 10000);

Returns:

• stateCount - Number of states currently stored
• taggedCount - Number of tagged states currently stored
• estimatedSizeKB - Rough estimation of memory usage in kilobytes

Note: Size estimation is approximate and based on JSON serialization size.

getTaggedState(tag: string): IState | undefined

Retrieves a tagged state by its tag name without affecting the current state.

// Create tagged states
store.updateState({ user: userData, $tag: "user-login" });
store.updateState({ cart: cartData, $tag: "checkout-ready" });

// Retrieve specific tagged states
const loginState = store.getTaggedState("user-login");
const checkoutState = store.getTaggedState("checkout-ready");

// Returns undefined for non-existent tags
const missing = store.getTaggedState("non-existent"); // undefined

Parameters:

• tag - The tag name to look up

Returns: Deep cloned tagged state or undefined if tag doesn't exist

getAvailableTags(): string[]

Returns an array of all available tag names.

store.updateState({ step: 1, $tag: "step-1" });
store.updateState({ step: 2, $tag: "step-2" });

console.log(store.getAvailableTags()); // ["step-1", "step-2"]

// Use for conditional navigation
if (store.getAvailableTags().includes("last-known-good")) {
  store.jumpToTag("last-known-good");
}

Returns: Array of tag names currently stored

jumpToTag(tag: string): void

Jumps to a tagged state, making it the current state and adding it to history.

// Create checkpoints
store.updateState({ page: "home", $tag: "home-page" });
store.updateState({ page: "profile", user: userData, $tag: "profile-page" });
store.updateState({ page: "settings" });

// Jump back to a checkpoint
store.jumpToTag("profile-page");
console.log(store.getCurrentState().page); // "profile"

// Continue from the restored state
store.updateState({ page: "edit-profile" });

Parameters:

• tag - The tag name to jump to

Throws: Error if the tag doesn't exist

Events: Emits TAG_JUMPED and STATE_UPDATED

removeTag(tag: string): boolean

Removes a tag from the tagged states collection.

store.updateState({ temp: "data", $tag: "temporary" });

const wasRemoved = store.removeTag("temporary");
console.log(wasRemoved); // true

// Tag is now gone
console.log(store.getTaggedState("temporary")); // undefined

Parameters:

• tag - The tag name to remove

Returns: true if tag was found and removed, false if it didn't exist

Events: Emits TAG_REMOVED for existing tags

clearTags(): void

Removes all tagged states from the collection.

// After bulk operations with many tags
store.clearTags();
console.log(store.getAvailableTags()); // []

// State history remains intact
console.log(store.stateStorage.length); // Still has all states

Events: Emits TAGS_CLEARED with count of cleared tags

Event Methods (Inherited from PubSub)

on(event: string, callback: Function): void

Subscribe to store events. Substate emits several built-in events for different operations.

Built-in Events:

| Event | When Emitted | Data Payload | |-------|--------------|--------------| | STATE_UPDATED | After any state update | newState: IState | | STATE_RESET | When resetState() is called | None | | TAG_JUMPED | When jumpToTag() is called | { tag: string, state: IState } | | TAG_REMOVED | When removeTag() removes an existing tag | { tag: string } | | TAGS_CLEARED | When clearTags() is called | { clearedCount: number } | | HISTORY_CLEARED | When clearHistory() is called | { previousLength: number } | | HISTORY_LIMIT_CHANGED | When limitHistory() is called | { newLimit: number, oldLimit: number, trimmed: number } |

// Listen to state updates
store.on('STATE_UPDATED', (newState: IState) => {
  console.log('State changed:', newState);
});

// Listen to tagging events
store.on('TAG_JUMPED', ({ tag, state }) => {
  console.log(`Jumped to tag: ${tag}`, state);
});

// Listen to memory management events
store.on('HISTORY_CLEARED', ({ previousLength }) => {
  console.log(`Cleared ${previousLength} states from history`);
});

// Listen to custom events
store.on('USER_LOGIN', (userData) => {
  console.log('User logged in:', userData);
});

emit(event: string, data?: unknown): void

Emit custom events to all subscribers.

// Emit custom event
store.emit('USER_LOGIN', { userId: 123, name: 'John' });

// Emit without data
store.emit('CACHE_CLEARED');

off(event: string, callback: Function): void

Unsubscribe from store events.

const handler = (state) => console.log(state);

store.on('UPDATE_STATE', handler);
store.off('UPDATE_STATE', handler); // Removes this specific handler

Store Properties

| Property | Type | Description | |----------|------|-------------| | name | string | Store identifier | | currentState | number | Index of current state in history | | stateStorage | IState[] | Array of all state versions | | defaultDeep | boolean | Default deep cloning setting | | maxHistorySize | number | Maximum number of states to keep in history | | beforeUpdate | UpdateMiddleware[] | Pre-update middleware functions | | afterUpdate | UpdateMiddleware[] | Post-update middleware functions |

Middleware Order

updateState(action) ├── store.beforeUpdate[] (store-wide) ├── State Processing │ ├── Clone state │ ├── Apply temp updates │ ├── Push to history │ └── Update tagged states ├── sync.beforeUpdate[] (per sync instance) ├── sync.afterUpdate[] (per sync instance) ├── store.afterUpdate[] (store-wide) └── emit STATE_UPDATED or $type event

🧠 Memory Management

Substate automatically manages memory through configurable history limits and provides tools for monitoring and optimization.

Automatic History Management

By default, Substate keeps the last 50 states in memory. This provides excellent debugging capabilities while preventing unbounded memory growth:

const store = createStore({
  name: 'AutoManagedStore',
  state: { data: [] },
  maxHistorySize: 50 // Default - good for most applications
});

// After 100 updates, only the last 50 states are kept
for (let i = 0; i < 100; i++) {
  store.updateState({ data: [i] });
}

console.log(store.stateStorage.length); // 50 (not 100!)

Memory Optimization Strategies

For Small Applications (Default)

// Use default settings - 50 states is perfect for small apps
const store = createStore({
  name: 'SmallApp',
  state: { user: null, settings: {} }
  // maxHistorySize: 50 (default)
});

For High-Frequency Updates

// Reduce history for apps with frequent state changes
const store = createStore({
  name: 'RealtimeApp',
  state: { liveData: [] },
  maxHistorySize: 10 // Keep minimal history
});

// Or dynamically adjust
if (isRealtimeMode) {
  store.limitHistory(5);
}

For Large State Objects

// Monitor and manage memory proactively
const store = createStore({
  name: 'LargeDataApp',
  state: { dataset: [], cache: {} },
  maxHistorySize: 20
});

// Regular memory monitoring
setInterval(() => {
  const { stateCount, estimatedSizeKB } = store.getMemoryUsage();
  
  if (estimatedSizeKB > 5000) { // Over 5MB
    console.log('Memory usage high, clearing history...');
    store.clearHistory();
  }
}, 30000);

For Debugging vs Production

const store = createStore({
  name: 'FlexibleApp',
  state: { app: 'data' },
  maxHistorySize: process.env.NODE_ENV === 'development' ? 100 : 25
});

// Runtime adjustment
if (debugMode) {
  store.limitHistory(200); // More history for debugging
} else {
  store.limitHistory(10);  // Minimal for production
}

Memory Monitoring

Use the built-in monitoring tools to track memory usage:

// Basic monitoring
function logMemoryUsage(store: ISubstate, context: string) {
  const { stateCount, estimatedSizeKB } = store.getMemoryUsage();
  console.log(`${context}: ${stateCount} states, ~${estimatedSizeKB}KB`);
}

// After bulk operations
logMemoryUsage(store, 'After data import');

// Regular health checks
setInterval(() => logMemoryUsage(store, 'Health check'), 60000);

Best Practices

1. 🎯 Choose appropriate limits: 50 states for normal apps, 10-20 for high-frequency updates
2. 📊 Monitor memory usage: Use getMemoryUsage() to track growth patterns
3. 🧹 Clean up after bulk operations: Call clearHistory() after large imports/updates
4. ⚖️ Balance debugging vs performance: More history = better debugging, less history = better performance
5. 🔄 Adjust dynamically: Use limitHistory() to adapt to different application modes

Performance Impact

The default settings are optimized for most use cases:

• Memory: ~50KB - 5MB typical usage depending on state size
• Performance: Negligible impact with default 50-state limit
• Time Travel: Full debugging capabilities maintained
• Automatic cleanup: No manual intervention required

💡 Note: The 50-state default is designed for smaller applications. For enterprise applications with large state objects or high-frequency updates, consider customizing maxHistorySize based on your specific memory constraints.

⚡ Performance Benchmarks

Substate delivers excellent performance across different use cases. Here are real benchmark results from our test suite (averaged over 5 runs for statistical accuracy):

🖥️ Test Environment: 13th Gen Intel(R) Core(TM) i7-13650HX (14 cores), 16 GB RAM, Windows 10 Home

🚀 Shallow State Performance

| State Size | Store Creation | Single Update | Avg Update | Property Access | Memory (50 states) | |------------|----------------|---------------|------------|-----------------|-------------------| | Small (10 props) | 41μs | 61μs | 1.41μs | 0.15μs | 127KB | | Medium (100 props) | 29μs | 63μs | 25.93μs | 0.15μs | 1.3MB | | Large (1000 props) | 15μs | 598μs | 254μs | 0.32μs | 12.8MB |

🏗️ Deep State Performance

| Complexity | Store Creation | Deep Update | Deep Access | Deep Clone | Memory Usage | |------------|----------------|-------------|-------------|------------|--------------| | Shallow Deep (1.2K nodes) | 52μs | 428μs | 0.90μs | 200μs | 10.4MB | | Medium Deep (5.7K nodes) | 39μs | 694μs | 0.75μs | 705μs | 45.8MB | | Very Deep (6K nodes) | 17μs | 754μs | 0.90μs | 788μs | 43.3MB |

📊 Key Performance Insights

• ⚡ Ultra-fast property access: Sub-microsecond access times regardless of state size
• 🔄 Efficient updates: Shallow updates scale linearly, deep cloning adds ~10-100x overhead (expected)
• 🧠 Smart memory management: Automatic history limits prevent unbounded growth
• 🎯 Consistent performance: Property access speed stays constant as state grows
• 📈 Scalable architecture: Handles 1000+ properties with <300μs update times

🏃‍♂️ Real-World Performance

// ✅ Excellent for high-frequency updates
const fastStore = createStore({
  name: 'RealtimeStore',
  state: { liveData: [] },
  defaultDeep: false // 1.41μs per update
});

// ✅ Great for complex nested state  
const complexStore = createStore({
  name: 'ComplexStore', 
  state: deepNestedObject,
  defaultDeep: true // 428μs per deep update
});

// ✅ Property access is always fast
const value = store.getProp('deeply.nested.property'); // ~1μs

🆚 Performance Comparison

| Operation | Substate | Native Object | Redux | Zustand | |-----------|----------|---------------|-------|---------| | Property Access | 0.15μs | ~0.1μs | ~2-5μs | ~1-3μs | | Shallow Update | 1.41μs | ~1μs | ~50-100μs | ~20-50μs | | Memory Management | Automatic | Manual | Manual | Manual | | History/Time Travel | Built-in | None | DevTools | None |

🔬 Benchmark Environment:

• Hardware: 13th Gen Intel(R) Core(TM) i7-13650HX (14 cores), 16 GB RAM
• OS: Windows 10 Home (Version 2009)
• Runtime: Node.js v18+
• Method: Averaged over 5 runs for statistical accuracy

Your results may vary based on hardware and usage patterns.

🔬 Performance Comparison Benchmarks

Substate includes comprehensive performance benchmarks comparing it with other popular state management libraries. These benchmarks provide scientifically accurate performance data based on real measurements, not estimates.

📊 What We Compare

• Substate - Our lightweight state management library
• Redux - Industry standard state management
• Zustand - Modern lightweight alternative
• Native JavaScript Objects - Baseline performance

🎯 Measured Metrics

• Store Creation - Time to initialize a new store/state
• Single Update - Time for individual state updates
• Batch Updates - Time for multiple updates in sequence
• Property Access - Time to read state properties
• Memory Usage - Estimated memory consumption

🚀 Running Comparison Benchmarks

# Run all comparison benchmarks
npm run test:comparison

# Generate comparison report
npm run test:comparison:report

# Run individual benchmarks
cd benchmark-comparisons
npm run benchmark:substate
npm run benchmark:redux
npm run benchmark:zustand
npm run benchmark:native

📈 Sample Results

Here's a sample comparison from our benchmark suite:

| Library | Property Access | Update Performance | Store Creation | Memory (Small State) | |---------|----------------|-------------------|----------------|---------------------| | Native JS | 47.90ns | 75.19ns | 525.13ns | 1KB | | Redux | 47.76ns | 78.20ns | 2.23μs | 61KB | | Zustand | 48.07ns | 78.62ns | 3.29μs | 61KB | | Substate | 61.42ns | 285.69ns | 5.45μs | 7KB |

🔬 Benchmark Methodology

✅ Fair Comparison:

• Identical test data across all libraries
• Same operations (store creation, updates, property access)
• Statistical rigor (5 runs per test with mean/median/min/max/std)
• Multiple state sizes (small: 10 props, medium: 100 props, large: 1000 props)

✅ Scientific Accuracy:

• Real measurements, not estimates
• Reproducible - anyone can run the same tests
• Comprehensive - tests multiple scenarios and metrics
• Transparent - full statistical analysis provided

📁 Results Storage

Benchmark results are automatically saved as JSON files in benchmark-comparisons/results/ with:

• Timestamped filenames for version tracking
• Complete statistical data (mean, median, min, max, standard deviation)
• Environment information (platform, Node.js version, CI status)
• Detailed breakdowns for each test scenario

📊 Report Generation

The report generator creates multiple output formats:

JSON Summary (performance-summary-latest.json):

• Consolidated averages from all libraries
• Structured data for programmatic analysis
• Environment metadata for reproducibility

Markdown Tables (performance-tables-latest.md):

• Ready-to-use markdown tables for documentation
• Formatted performance comparisons with proper units
• Best performance highlighted in bold for easy identification
• Performance insights and recommendations
• Can be directly included in README files or documentation

Console Output:

• Real-time display of comparison results
• Detailed statistical breakdowns for each library
• Performance insights and fastest metrics identification

🎯 Key Insights

• Native JavaScript: Fastest raw performance, no overhead
• Substate: Optimized for reactive state with minimal overhead (~5x slower than native)
• Zustand: Good balance of features and performance
• Redux: More overhead due to action/reducer pattern

📊 Use Case Recommendations

• High-frequency updates: Consider Native JS or Substate
• Complex state logic: Redux provides predictable patterns
• Simple state management: Zustand offers good balance
• Reactive features needed: Substate provides built-in Pub/Sub

💡 Note: Performance varies by use case. Choose based on your specific requirements, not just raw speed. The comparison benchmarks help you make informed decisions based on real data.

📊 Latest Results: The most recent benchmark results are available in benchmark-comparisons/results/performance-tables-latest.md and can be included directly in documentation.

🔄 Why Choose Substate?

Comparison with Other State Management Solutions

| Feature | Substate | Redux | Zustand | Valtio | MobX | |---------|----------|-------|---------|--------|------| | Bundle Size | ~11KB | ~4KB | ~2KB | ~7KB | ~63KB | | TypeScript | ✅ Excellent | ✅ Excellent | ✅ Excellent | ✅ Excellent | ✅ Excellent | | Learning Curve | 🟢 Low | 🔴 High | 🟢 Low | 🟡 Medium | 🔴 High | | Boilerplate | 🟢 Minimal | 🔴 Heavy | 🟢 Minimal | 🟢 Minimal | 🟡 Some | | Time Travel | ✅ Built-in | ⚡ DevTools | ❌ No | ❌ No | ❌ No | | Memory Management | ✅ Auto + Manual | ❌ Manual only | ❌ Manual only | ❌ Manual only | ❌ Manual only | | Immutability | ✅ Auto | ⚡ Manual | ⚡ Manual | ✅ Auto | ❌ Mutable | | Sync/Binding | ✅ Built-in | ❌ No | ❌ No | ❌ No | ✅ Yes | | Framework Agnostic | ✅ Yes | ✅ Yes | ✅ Yes | ✅ Yes | ✅ Yes | | Middleware Support | ✅ Simple | ✅ Complex | ✅ Yes | ✅ Yes | ✅ Yes | | Nested Updates | ✅ Dot notation + Object spread | ⚡ Reducers | ⚡ Manual | ✅ Direct | ✅ Direct | | Tagged States | ✅ Built-in | ❌ No | ❌ No | ❌ No | ❌ No |

NOTE: Clone our repo and run the benchmarks to see how we stack up!

💡 About This Comparison:

• Bundle sizes are approximate and may vary by version
• Learning curve and boilerplate assessments are subjective and based on typical developer experience
• Feature availability is based on core functionality (some libraries may have community plugins for additional features)
• Middleware Support includes traditional middleware, subscriptions, interceptors, and other extensibility patterns
• Performance data is based on our benchmark suite - run npm run test:comparison for current results

When to Use Substate

✅ Perfect for:

• Any size application that needs reactive state with automatic memory management
• Rapid prototyping where you want full features without configuration overhead
• Projects requiring unidirectional data binding (unique sync functionality)
• Applications with complex nested state (dot notation updates)
• Teams that want minimal setup with enterprise-grade features
• Long-running applications where memory management is critical
• Time-travel debugging and comprehensive state history requirements
• High-frequency updates with configurable memory optimization

✅ Especially great for:

• Real-time applications (automatic memory limits prevent bloat)
• Form-heavy applications (sync functionality + memory management)
• Development and debugging (built-in time travel + memory monitoring)
• Production apps that need to scale without memory leaks

⚠️ Consider alternatives for:

• Extremely large enterprise apps with complex distributed state (consider Redux + RTK for strict patterns)
• Teams requiring specific architectural constraints (Redux enforces stricter patterns)
• Projects already heavily invested in other state solutions with extensive tooling

Migration Benefits

From Redux:

• 🎯 Significantly less boilerplate - No action creators, reducers, or complex setup
• 🔄 Built-in time travel without DevTools dependency
• 🧠 Automatic memory management - No manual cleanup required
• 🎪 Simpler middleware system with before/after hooks
• 📊 Built-in monitoring tools for performance optimization

From Context API:

• ⚡ Better performance with granular updates and memory limits
• 🕰️ Built-in state history with configurable retention
• 🔗 Advanced synchronization capabilities (unique to Substate)
• 📦 Smaller bundle size with more features
• 🧠 No memory leaks from unbounded state growth

From Zustand:

• 🔗 Unique sync functionality for unidirectional data binding
• 🕰️ Complete state history with automatic memory management
• 🎯 Built-in TypeScript support with comprehensive types
• 🌳 Flexible nested property handling with dot notation
• 📊 Built-in memory monitoring and optimization tools

From Vanilla State Management:

• 🏗️ Structured approach without architectural overhead
• 🔄 Automatic immutability and history tracking
• 🧠 Memory management prevents common memory leak issues
• 🛠️ Developer tools built-in (no external dependencies)

🎯 What Makes Substate Unique

Substate is one of the few state management libraries that combines all these features out of the box:

1. 🔗 Built-in Sync System - Unidirectional data binding with middleware transformations
2. 🧠 Intelligent Memory Management - Automatic history limits with manual controls
3. 🕰️ Zero-Config Time Travel - Full debugging without external tools
4. 🏷️ Tagged State Checkpoints - Named snapshots for easy navigation
5. 📊 Performance Monitoring - Built-in memory usage tracking
6. 🌳 Flexible Nested Updates - Intuitive nested state management with dot notation or object spread
7. ⚡ Production Ready - Optimized defaults that scale from prototype to enterprise

💡 Key Insight: Most libraries make you choose between features and simplicity. Substate gives you enterprise-grade capabilities with a learning curve measured in minutes, not weeks.

📋 TypeScript Definitions

Core Interfaces

interface ISubstate extends IPubSub {
  name: string;
  afterUpdate: UpdateMiddleware[];
  beforeUpdate: UpdateMiddleware[];
  currentState: number;
  stateStorage: IState[];
  defaultDeep: boolean;
  
  getState(index: number): IState;
  getCurrentState(): IState;
  getProp(prop: string): unknown;
  resetState(): void;
  updateState(action: IState): void;
  sync(config: ISyncConfig): () => void;
}

interface ICreateStoreConfig {
  name: string;
  state?: object;
  defaultDeep?: boolean;
  beforeUpdate?: UpdateMiddleware[];
  afterUpdate?: UpdateMiddleware[];
}

interface IState {
  [key: string]: unknown;
  $type?: string;
  $deep?: boolean;
}

interface ISyncConfig {
  readerObj: Record<string, unknown>;
  stateField: string;
  readField?: string;
  beforeUpdate?: BeforeMiddleware[];
  afterUpdate?: AfterMiddleware[];
}

Middleware Types

// Primary state type - represents any state object with optional keywords
type TSubstateState = object & TStateKeywords;

// Update middleware for state changes
type TUpdateMiddleware = (store: ISubstate, action: Partial<TSubstateState>) => void;

// Sync middleware for unidirectional data binding
type TSyncMiddleware = (value: unknown, context: ISyncContext, store: ISubstate) => unknown;

// Sync configuration with middleware support
type TSyncConfig = {
  readerObj: Record<string, unknown> | object;
  stateField: string;
  readField?: string;
  beforeUpdate?: TSyncMiddleware[];
  afterUpdate?: TSyncMiddleware[];
  syncEvents?: string[] | string;
};

// Context provided to sync middleware
interface ISyncContext {
  source: string;
  field: string;
  readField: string;
}

// State keywords for special functionality
type TStateKeywords = {
  $type?: string;
  $deep?: boolean;
  $tag?: string;
  [key: string]: unknown;
};

📈 Migration Guide

Version 10.x Migration

Substate v10 introduces several improvements and breaking changes. Here's how to upgrade:

Breaking Changes

1. Import Changes

// ❌ Old (v9)
import Substate from 'substate';

// ✅ New (v10)
import { createStore, Substate } from 'substate';

2. Store Creation

// ❌ Old (v9)
const store = new Substate({ name: 'MyStore', state: { count: 0 } });

// ✅ New (v10) - Recommended
const store = createStore({ name: 'MyStore', state: { count: 0 } });

// ✅ New (v10) - Still works but not recommended
const store = new Substate({ name: 'MyStore', state: { count: 0 } });

3. Peer Dependencies

# Install peer dependencies
npm install clone-deep object-bystring

New Features in v10

• Sync Method: Unidirectional data binding with middleware
• Enhanced TypeScript: Better type inference and safety
• Improved Performance: Optimized event handling and state updates
• Better Tree Shaking: Only import what you use

Migration Steps

1. Update imports and installation

npm install substate@10 clone-deep object-bystring

2. Replace direct instantiation with createStore

// Before
const stores = [
  new Substate({ name: 'Store1', state: { data: [] } }),
  new Substate({ name: 'Store2', state: { user: null } })
];

// After  
const stores = [
  createStore({ name: 'Store1', state: { data: [] } }),
  createStore({ name: 'Store2', state: { user: null } })
];

3. Leverage new sync functionality

// New capability - sync store to UI models
const unsync = store.sync({
  readerObj: uiModel,
  stateField: 'user.profile',
  readField: 'userInfo'
});

From Other Libraries

From Redux

// Redux setup
const store = createStore(rootReducer);
store.dispatch({ type: 'INCREMENT', payload: 1 });

// Substate equivalent
const store = createStore({ name: 'Counter', state: { count: 0 } });
store.updateState({ count: store.getProp('count') + 1 });

From Zustand

// Zustand
const useStore = create((set) => ({
  count: 0,
  increment: () => set((state) => ({ count: state.count + 1 }))
}));

// Substate
const store = createStore({ name: 'Counter', state: { count: 0 } });
const increment = () => store.updateState({ 
  count: store.getProp('count') + 1 
});

🔧 Troubleshooting

Common Issues and Solutions

🔄 State Updates Not Triggering Re-renders

Problem: State updates aren't triggering component re-renders or event listeners.

Solutions:

// ✅ Correct: Use updateState method
store.updateState({ count: 1 });

// ❌ Wrong: Direct state mutation
store.stateStorage[store.currentState].count = 1; // Won't trigger events

// ✅ Correct: Subscribe properly
store.on('UPDATE_STATE', (newState) => {
  console.log('State changed:', newState);
  // Update your UI here
});

🧊 Deep Cloning Issues

Problem: Performance issues with deep cloning on complex objects.

Solutions:

// For simple updates, disable deep cloning
store.updateState({
  simpleValue: 'new value',
  $deep: false  // Skip deep cloning for this update
});

// Or configure store to skip deep cloning by default
const store = createStore({
  name: 'FastStore',
  state: { data: largeObject },
  defaultDeep: false  // Skip deep cloning by default
});

// Force deep cloning when needed
store.updateState({
  complexData: largeObject,
  $deep: true  // Force deep cloning
});

🔗 Sync Not Working

Problem: Sync bindings aren't updating target objects.

Solutions:

// ✅ Correct sync setup
const unsync = store.sync({
  readerObj: targetObject,
  stateField: 'user.name',
  readField: 'displayName'
});

// Make sure to call unsync() when component unmounts
useEffect(() => {
  return () => unsync(); // Cleanup sync binding
}, []);

// Check that property paths exist
console.log(store.getProp('user.name')); // Should not be undefined

🏷️ Tagged States Not Found

Problem: jumpToTag() throws "tag not found" error.

Solutions:

// ✅ Correct tag creation
store.updateState({
  data: important