ryansolid / Mobx Jsx
Programming Languages
MobX JSX
This library is a demonstration of how MobX fine grain control can be leveraged directly in JSX for considerably better performance than pairing it with a Virtual DOM library. Even the fastest Virtual DOM library will have overhead when reconciling many small discreet changes into a scheduled render and patch.
Check out MobX JSX performance near the top of the charts on the JS Frameworks Benchmark.
It accomplishes this with using Babel Plugin JSX DOM Expressions. It compiles JSX to DOM statements and wraps expressions in functions that can be called by the library of choice. In this case autorun
wraps these expressions ensuring the view stays up to date. Unlike Virtual DOM only the changed nodes are affected and the whole tree is not re-rendered over and over.
Usage
To use call render as follow
import { render } from 'mobx-jsx';
render(App, document.getElementById('main'));
And include 'babel-plugin-jsx-dom-expressions' in your babelrc, webpack babel loader, or rollup babel plugin.
"plugins": [["babel-plugin-jsx-dom-expressions", {moduleName: 'mobx-jsx'}]]
See plugin options
For TS JSX types add to your tsconfig.json
:
"jsx": "preserve",
"jsxImportSource": "mobx-jsx"
Installation
> npm install mobx-jsx babel-plugin-jsx-dom-expressions
Examples
API
MobX JSX works both with function and Class components (extend Component from this library).
Map For Observable Arrays
Ships a specialize map function for optimal list rendering that takes an observable array as it's first argument. To avoid re-rendering the complete list on changes.
import { map } from "mobx-jsx";
const list = observable(["Alpha", "Beta", "Gamma"]);
<ul>{
map(list, item => <li>{item}</li>)
}</ul>
Lifecycles
Unlike React render
only runs once, so you may not need to split in functions or methods your Lifecycles, all the initialization code could be set on render
. See the issue Lifecycles for furter information
However, you may emulate componentDidMount
and componentWillUnmount
. The microtakPromise
resolution will be after mount and cleanup
runs at the beginning of re-evaluation so the elements aren't removed yet.
Example
import { render, cleanup, Component as _Component } from 'mobx-jsx'
class Component extends _Component {
constructor(props) {
super(props)
if (this.componentDidMount) {
Promise.resolve().then(() => this.componentDidMount())
}
if (this.componentWillUnmount) {
cleanup(() => this.componentWillUnmount())
}
}
}
class App extends Component {
componentDidMount(){ console.log('componentDidMount')}
componentWillUnmount(){ console.log('componentWillUnmount') }
}
Lazily Loading a Component
import { render, lazy } from "mobx-jsx";
// use lazy to allow code splitting
const SomeComponent = lazy(() => import("./SomeComponent"));
function App() {
return (
<>
<SomeComponent name={"John"} />
</>
);
}
render(App, document.body);
MobX JSX also supports a Context API.
Non-precompiled environments
Alternatively supports Tagged Template Literals or HyperScript for non-precompiled environments by installing the companion library and including variants:
import { html } from 'mobx-jsx/html'; // or
import { h } from 'mobx-jsx/h';
There is a small performance overhead of using these runtimes but the performance is still very impressive. Tagged Template solution is much more performant that the HyperScript version, but HyperScript opens up compatibility with some companion tooling like:
- HyperScript Helpers Use an element as functions DSL
- Babel Plugin HTM Transpile Tagged Template Literals to HyperScript for IE11 compatibility
Further documentation available at: Lit DOM Expressions and Hyper DOM Expressions.