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Haxe-React #next: preparing for 2.0.0
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.gitignore Start react-next releases Sep 24, 2018
haxelib.json 1.101.0 - ReactComponent builders with keys Oct 7, 2018

Haxe React #next temp fork (See Roadmap)

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A Haxe library offering externs and tool functions leveraging Haxe's excellent type system and compile time macros to offer a strongly typed language to work with the increasingly popular React library.

haxelib install react-next

⚠️ Warning: outdated

This readme needs many updates. See changes in #next; other docs available in doc folder.

What's included / not included

This library covers React core and ReactDOM. It does NOT cover: ReactAddOns, react-router or React Native.

We recommend looking into / contributing to the following efforts:

Application architecture examples

React doesn't enforce any specific application architecture; here are a few approaches:

Redux, a very popular new approach of Model-View-Intent architecture: global state object, following immutability principles, but the wiring has been re-imagined to use the best of Haxe:

MMVC, classic, battle tested, Model-View-Mediator with state of the art Dependency Injection:

Flux, inspired by Facebook's suggested architecture for React; this is a very quick PoC which probably won't scale well to complex apps, but it shows a good range of React features:

Support / discussions

If you have questions / issues, join haxe-react on


Most of the regular React API is integrated (non-JSX example):

import react.React;
import react.ReactDOM;

class App extends ReactComponent {

	static public function main() {
		ReactDOM.render(React.createElement(App), Browser.document.getElementById('app'));

	public function new() {

	override function render() {
		var cname = 'foo';
		return React.createElement('div', {className:cname}, [/*children*/]);

Note that React.createElement strictly expects either a String, a Function, or a class extending ReactComponent. It includes when writing externs for 3rd party JS libraries you must specify extends:

@:jsRequire('react-redux', 'Provider')
extern class Provider extends react.ReactComponent { }


The Haxe compiler (and editors) doesn't allow to use exactly the JSX XML DSL, so we had to compromise a bit...

This library's take on JSX is to use a compile-time macro to parse JSX as a string to generate the same kind of code that Facebook's JSX, Babel and Typescript will generate.

Both classic JSX {} binding and Haxe string interpolation $var / ${expression} / <$Comp> are allowed. The advantage of string interpolation is Haxe editor supports for completion and code navigation.

Spread operator and complex expressions within curly braces are supported.

import react.React;
import react.ReactDOM;
import react.ReactMacro.jsx;

class App extends ReactComponent {

	static public function main() {
		ReactDOM.render(jsx('<App/>'), Browser.document.getElementById('app'));

	public function new() {

	override function render() {
		var cname = 'foo';
		return jsx('
			<div className=$cname>
				<App.statelessComponent style=${{margin:"10px"}}/>

	static function statelessComponent(props:Dynamic) {
		return jsx('<div {...props}/>');

JSX Fragments

Fragments (React 16.2+) let you group a list of children without adding extra nodes to the DOM.

Two syntaxes are supported:

    <span>more text</span>
    Still more text

// or short syntax:
    <span>more text</span>
    Still more text

JSX gotchas

  1. JSX is not String magic! Do not concatenate Strings to construct the JSX expression

  2. Haxe's JSX parser is not "re-entrant"

    In JavaScript you can nest JSX inside curly-brace expressions:

    return (
        <div>{ isA ? <A/> : <B/> }</div>

    However this isn't allowed in Haxe, so you must extract nested JSX into variables:

    var content = isA ? jsx('<A/>') : jsx('<B/>');
    return jsx('<div>{content}</div>');

Components strict typing

The default ReactComponent type is a shorthand for ReactComponentOf<Dynamic, Dynamic, Dynamic>, a fully untyped component.

To fully benefit from Haxe's strict typing you should look into extending a stricter base class:

typedef ReactComponentOfProps<TProps> = ReactComponentOf<TProps, Empty>;
typedef ReactComponentOfState<TState> = ReactComponentOf<Empty, TState>;
typedef ReactComponentOfPropsAndState<TProps, TState> = ReactComponentOf<TProps, TState>;

React JS dependency

There are 2 ways to link the React JS library:

Require method (default)

By default the library uses require('react') to reference React JS.

This means you are expected to use npm to install this dependency:

npm install react

and a second build step to generate the final JS file, for instance using browserify:

npm install browserify
browserify haxe-output.js -o final-output.js

(note that you can use watchify to automatically run this build step)

Global JS

The other common method is to download or reference the CDN files of React JS in your HTML page:

<script src="//"></script>
<script src="//"></script>

and don't forget to add the following Haxe define to your build command:

-D react_global

Look at samples/todoapp for an example of this approach.

JSX Optimizing Compiler

Inline ReactElements

By default, when building for release (eg. without -debug), calls to React.createElement are replaced by inline JS objects (if possible).


// regular
return React.createElement('div', {key:'bar', className:'foo'});

// inlined (simplified)
return {$$typeof:Symbol.for('react.element'), type:'div', props:{className:'foo'}, key:'bar'}

This behaviour can be disabled using -D react_no_inline.

Optimization tools

Avoidable renders warning

Setting -D react_render_warning will enable runtime warnings for avoidable renders.

This will add a componentDidUpdate (or update the existing one) where a shallowCompare is done on current and previous props and state. If both did not change, a warning will be displayed in the console.

False positives can happen if your props are not flat, due to the shallowCompare.

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