PreffX is a self-confident JS library for creating reactive DOM. It is inspired by React and Preact, but offers its own signal-based approach.

⚠️ The project is currently in an experimental stage, do not use in a production environment. ⚠️

Basic principles

• React-like JSX syntax;
• Preact signals as reactivity core;
• only signals cause rerender;
• each component is executed only once;
• component props come as the first argument and all utilities come as the second argument - there is no need to import them,
• both sync and async function components support;
• distinction between properties and attributes (all properties are prefixed with $) - for example, $value is a property, and value is an attribute.

Links

• Docs (in development)
• SourceCraft
• GitHub
• NPM

Installation

You can use degit:

npx degit msabitov/vite-preffx preffx-starter 
cd preffx-starter         
npm install        
npm run dev

You can also try StackBlitz demo

Examples

• Simple counter:

import type { PC } from 'preffx';

export const App: PC = (props, { signal }) => {
    const count = signal(0);
    return <button
        onClick={() => {
            count.value += 1
        }}
    >
        Count is {count}
    </button>
};

• How to create element refs:

import type { PC } from 'preffx';

export const App: PC = (props, { signal }) => {
    const signalRef = signal();
    return <div $ref={signalRef}>
        <div
          $ref={(refVal) => {
            // it will be called after element mounted with refVal = HTMLDivElement
            // and before element destroyed with refVal = null
          }}
        >
            Refs
        </button>
    </div>
};

• Lifecycle hooks:

import type { PC } from 'preffx';

export const App: PC = (props, { onMount, onDestroy }) => {
    const { count } = props;

    onMount(() => {
        // some mount logic
    });
    
    onDestroy(() => {
        // some destroy logic
    });
    return <button
        onClick={() => {
            count.value += 1
        }}
    >
        Count is {count}
    </button>
};

• List rendering:

import type { PC } from 'preffx';

export const App: PC = (props, { For }) => {
    const items = signal([
        {
            name: 'First'
        },
        {
            name: 'Second'
        }
    ]);

    return <ul>
        <For
            items={items}
            callback={(item) => <li>Item with name: {item.name}</li>}
            fallback={<li>No items</li>}
        />
    </ul>;
};

• Context handling:

import type { PC } from 'preffx';

const contextKey = 'ctx-counter';

const AnotherComponent: PC = (props, { context }) => {
    // read context
    const counter = context[contextKey];
    return <span>
        {counter}
    </span>;
};

export const App: PC = (props, { signal, context }) => {
    const counter = signal(0);
    // modify context
    context[contextKey] = counter;
    return <p>
        {valueFromContext}
        <AnotherComponent />
    </p>;
};

• Async components:

import type { APC } from 'preffx';
import { getData } from './data';
import { AnotherComponent, AnotherAsyncComponent } from './components';

const AsyncComponent: APC<{
    name: string;
}> = async (props, utils) => {
    const data = await getData()
    const componentRoot = await <AnotherAsyncComponent name='nested'/>;
    return <div>
        <AnotherComponent data={data} />
        {componentRoot}
    </div>;
}

• Error handling:

import type { PC } from 'preffx';
import { AnotherComponent } from './components';

export const App: PC = (props, { Catch }) => {
    return <div>
        Sometimes components return errors
        <Catch fallback={<div>Catched!</div>}>
            <AnotherComponent />
        </Catch>
    </div>;
};

• Defered value handling:

import type { PC } from 'preffx';
import { AsyncComponent } from './components';

export const App: PC = (props, { computed, Defer }) => {
    const def = computed(() => <AsyncComponent id={props.id} />);
    return <Defer
        value={def}
        initial={<div>Please wait</div>}
    />;
};

• Portal:

import type { PC } from 'preffx';

export const App: PC = (props, { Portal }) => {
    return <>
        <span>Some text inside current tree</span>
        <Portal root={document.getElementById('portal')}>
            <div>Text inside portal</div>
        </Portal>
    </>;
};

• Unique identifiers:

import type { PC } from 'preffx';

export const App: PC = (props, { id }) => {
    // get unique id
    const inputId = id();
    return <>
        <label>
            Password:
            <input
                type="password"
                aria-describedby={inputId}
            />
        </label>
        <p id={inputId}>
            The password should contain at least 18 characters
        </p>
    </>;
};