simple-state

Simple state management for JavaScript applications.

Installation

$ yarn add @imjoehaines/simple-state
# OR
$ npm install @imjoehaines/simple-state

Usage

import createStore from 'simple-state'

const initialState = { amount: 1 }

const modelConstructor = setState => ({
  increment () {
    setState(state => ({ ...state, amount: state.amount + 1 }))
  }
})

const store = createStore(initialState, modelConstructor)

console.log(store.getState()) // { amount: 1 }

store.increment()

console.log(store.getState()) // { amount: 2 }

simple-state exports a single function, createStore, which takes some initial state and a model constructor as arguments.

Initial state

The initial state of your application can be any plain JavaScript object. It's simply passed to your model when an action is called, so the structure doesn't matter to simple-state.

Model constructor

A model constructor is a function that returns a model when called. It takes a setState function as an argument and uses that inside actions to make changes to state.

Model constructors look like this

const modelConstructor = setState => ({
  increment () {
    setState(state => ({ ...state, amount: state.amount + 1 }))
  }
})

// OR

function modelConstructor (setState) {
  return {
    increment: function () {
      setState(state => ({ ...state, amount: state.amount + 1 }))
    }
  }
}

Each of the functions in the object that a model constructor returns will be available as functions on the store created by createStore. For example, in this case we would have a store.increment function as our model constructor includes this.

The setState function takes a callback which should return the updated state, based on the state argument it is provided.

Actions

An action is the name given to any function inside a model.

increment () {
  setState(state => ({ ...state, amount: state.amount + 1 }))
}

All actions will be available as functions on the store.

Listeners

The store also provides a listen function which can be used to listen for any state changes caused by actions. It accepts a callback function, which takes no arguments and will be called whenever an action is.

Any number of listeners can be attached to a store.

const store = createStore({ amount: 1 }, setState => ({
  increment () {
    setState(state => ({ ...state, amount: state.amount + 1 }))
  }
}))

store.listen(() => {
  console.log('listener one', store.getState())
})

store.listen(() => {
  console.log('listener two', store.getState())
})

store.listen(() => {
  console.log('listener three', store.getState())
})

Actions can be called from within a listener, but you should be careful not to create an infinite loop of action → listener → action.