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React & JSX Cheatsheet

React & JSX Cheatsheet

Overview
JSX HTML <div>...</div>
JSX Component <Component property={javascript} />
<Component property='string' />
JSX Component with Children <Component>{children}</Component>
reference: props.children
Escaping JavaScript {...}
require statements const React = require('react');
const ReactDOM = require('react-dom');
npm modules react, react-dom
Render in DOM ReactDOM.render(<MyApp />, document.getElementById('root'));
Functional components function MyComponent(props) { return <div>...</div> }
Base class for class components React.Component
First statement in constructor super(props)
Initializing state this.state={...}
Setting state this.setState({...})
Referring previous state this.setState(prevState => ({...}))
this.setState((prevState, props) => ({...}))

Functional Component

'use strict';

const React = require('react');

function Greeting(props) {
   return (
      <h1>{props.salutation + ' ' + props.who + '!'}</h1>
   );
}
const world='world';

<Greeting salutation='hello' who={world} />

Class Component with State

class MyComponent extends React.Component {
   constructor(props) {
      super(props);
      this.state = {property: 'initial'};
      this.handleClick = this.handleClick.bind(this);
   }
   render() {
      return (
         <div>
            <button onClick={this.handleClick}>Click me!</button>
            <div>{this.state.property}</div>
         </div>
      );
   }
   handleClick() {
      this.setState({property: 'clicked'});
   }
}

Render React Component in DOM

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>React is cool!</title>
  </head>
  <body>
    <div id="root"></div>
    <script src="https://example.com/transformed-with-babel.js"></script>
  </body>
</html>
'use strict';

const React = require('react');
const ReactDOM = require('react-dom');
const MyCoolApp = require('./my-cool-app.js');

ReactDOM.render(
   <MyCoolApp />,
   document.getElementById('root')
);

Component with Children

const borderStyle = {
   border: '1px solid darkcyan',
   boxShadow: '5px 5px 5px gray',
   margin: '10px',
   padding: '5px'
};

function Border(props) {
   return (
      <div style={borderStyle}>
         {props.children}
      </div>
   );
}

HTML vs Web API vs React JSX

Difference HTML Web API React JSX
Names of attributes / properties lower case (mostly) camelCase camelCase
Values of attributes / properties string expression expression within { }
Names of event handlers (on...) lower case lower case (!) camelCase
Values of event handlers (on...) JavaScript string function expr. function expr. within { }
Event Handlers: prevent default behaviour n/a can return false must call event.preventDefault();
HTML Tags lower case n/a* lower case
Custom Tags (Components) n/a n/a start with capital letter

*Represented by API objects and interfaces like Document, HTMLDivElement, ...

Examples

HTML Attribute HTML Example JSX Property JSX Example
class <div class='fancy'>...</div> className* <div className='fancy'>...</div>
onclick <button onclick="foo()">... onClick* <button onClick={foo}>...
<button onClick={() => foo(param)}>...
tabindex <input tabindex=2 /> tabIndex <input tabIndex={2} />

*Note: className is identical to the Web API, while onClick is not!
See also on MDN web docs: Element, HTMLElement, GlobalEventHandlers

Special Tags

Tag HTML behaviour React behaviour
<textarea> content defined by children content defined by value attribute
<select> and <option> selection defined by presence of selected attribute on <option> selection defined by value attribute on <select>

Inline CSS vs React Inline Style

Difference Inline CSS React Inline Style
The style Attribute / Property a string enclosed by " or ' an object eclosed by { }
Name of style properties lower case with hyphen - camelCase
Value of style properties CSS expression (textual) JavaScript expression
Separator ; ,
Can be merged no yes, e.g. with Object.assign()
Can use variables no yes

Examples

CSS Property CSS Inline Style Example React Style Property React Inline Style Example
background-color style="background-color: green" backgroundColor style={{backgroundColor: 'green'}}
border style="border: 1px solid black" border style={{border: '1px solid black'}}
border-style,
border-width
style='border-style: solid; border-width: 5' borderStyle,
borderWidth
style={{borderStyle: 'solid', borderWidth: 5}}

Lifecycle Methods

Lifecycle Method
Before component gets unmounted componentWillUnmount()
After component got mounted componentDidMount()
Before is updated (receives new state or props) componentWillUpdate(nextProps, nextState)
After component was updated componentDidUpdate(prevProps, prevState)

Tips & Tricks

Make this available in event handler in constructor: this.handleEvent = this.handleEvent.bind(this);
Use id in loop <button onClick={(e) => this.method(id, e)}>... or
<button onClick={this.method.bind(this, id)}>...
Conditional rendering: Logical && Operator {condition && <SomeComponent>...}
Conditional rendering: Ternary Operator {condition ? (<TrueComponent>...) : (<FalseComponent>...)}
Prevent component from rendering return null in render() method / component function
Prevent navigation href="#"
<a href="#" onClick={...}>...</a>
Reuse event handler for multiple HTML elements Assign a custom name attribute and evaluate that attribute
with event.target.name in event handler. See: React Quick Start

Babel

Preset: react

Manual Transformation

const babel = require('babel-core');
let transformed = babel.transform(code, {"presets": ["react"]}).code;

CSS for Full Page

html, body, #root {
   margin: 0;
   height: 100%;
   width: 100%;
}
@mnezmah

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commented Aug 28, 2018

Very cool, than you very much :)

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