Fre
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Concurrent Mode β This is an amazing idea, which implements the coroutine scheduler in JavaScript, it also called Time slicing.
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O(ND) reconcilation algorithm β Fre has a minimal longest-increasing-subsequence algorithm, It supported keyed, pre-process.
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Do more with less β After tree shaking, project of hello world is only 1KB, but it has most features, virtual DOM, hooks API, Fragments and so on.
Sponsors
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Contributors
Use
yarn add freimport { render, useState } from 'fre'
function App() {
const [count, setCount] = useState(0)
return <>
<h1>{count}</h1>
<button onClick={() => setCount(count + 1)}>+</button>
</>
}
render(<App/>, document.body)Hooks API
useState
useState is a base API, It will receive initial state and return an Array
You can use it many times, new state is available when component is rerender
function App() {
const [up, setUp] = useState(0)
const [down, setDown] = useState(0)
return (
<>
<h1>{up}</h1>
<button onClick={() => setUp(up + 1)}>+</button>
<h1>{down}</h1>
<button onClick={() => setDown(down - 1)}>-</button>
</>
)
}useReducer
useReducer and useState are almost the sameοΌbut useReducer needs a global reducer
function reducer(state, action) {
switch (action.type) {
case 'up':
return { count: state.count + 1 }
case 'down':
return { count: state.count - 1 }
}
}
function App() {
const [state, dispatch] = useReducer(reducer, { count: 1 })
return (
<>
{state.count}
<button onClick={() => dispatch({ type: 'up' })}>+</button>
<button onClick={() => dispatch({ type: 'down' })}>-</button>
</>
)
}useEffect
It is the execution and cleanup of effects, which is represented by the second parameter
useEffect(f) // effect (and clean-up) every time
useEffect(f, []) // effect (and clean-up) only once in a component's life
useEffect(f, [x]) // effect (and clean-up) when property x changes in a component's life
function App({ flag }) {
const [count, setCount] = useState(0)
useEffect(() => {
document.title = 'count is ' + count
}, [flag])
return (
<>
<h1>{count}</h1>
<button onClick={() => setCount(count + 1)}>+</button>
</>
)
}If it returns a function, the function can do cleanups:
useEffect(() => {
document.title = 'count is ' + count
return () => {
store.unsubscribe()
}
}, [])useLayout
More like useEffect, but useLayout is sync and blocking UI.
useLayout(() => {
document.title = 'count is ' + count
}, [flag])useMemo
useMemo has the same rules as useEffect, but useMemo will return a cached value.
const memo = (c) => (props) => useMemo(() => c, [Object.values(props)])useCallback
useCallback is based useMemo, it will return a cached function.
const cb = useCallback(() => {
console.log('cb was cached.')
}, [])useRef
useRef will return a function or an object.
function App() {
useEffect(() => {
console.log(t) // { current:<div>t</div> }
})
const t = useRef(null)
return <div ref={t}>t</div>
}If it uses a function, it can return a cleanup and executes when removed.
function App() {
const t = useRef((dom) => {
if (dom) {
doSomething()
} else {
cleanUp()
}
})
return flag && <span ref={t}>I will removed</span>
}Fragments
// fragment
function App() {
return <>{something}</>
}
// render array
function App() {
return [a, b, c]
}jsx2
plugins: [
[
'@babel/plugin-transform-react-jsx',
{
runtime: 'automatic',
importSource: 'fre',
},
],
]Compare with other frameworks
The comparison is difficult because the roadmap and trade-offs of each framework are different, but we have to do so.
- react
React is the source of inspiration for fre. Their implementation and asynchronous rendering are similar. The most amazing thing is concurrent mode, which means that react and fre have the same roadmap -- Exploring concurrent use cases.
But at the same time, fre has obvious advantages in reconciliation algorithm and bundle size.
- vue / preact
To some extent, vue and preact are similar. They have similar synchronous rendering, only the API is different.
The reconciliation algorithm of fre is similar to vue3, but the biggest difference is that vue/preact do not support concurrent mode, this means that the roadmap is totally different.
| framework | concurrent | offscreen | reconcilation algorithm | bundle size |
|---|---|---|---|---|
| fre2 | β | β | β β β β | 2kb |
| react18 | β | β | β β | 43kb |
| vue3 | Γ | x | β β β β β | 33kb |
| preactX | Γ | x | β β β | 4kb |
License
MIT @yisar
