340 lines
16 KiB
JavaScript
340 lines
16 KiB
JavaScript
/* *******************************************************************************************
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* REACT.JS CHEATSHEET
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* DOCUMENTATION: https://reactjs.org/docs/
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* FILE STRUCTURE: https://reactjs.org/docs/faq-structure.html
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* ******************************************************************************************* */
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```
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npm install --save react // declarative and flexible JavaScript library for building UI
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npm install --save react-dom // serves as the entry point of the DOM-related rendering paths
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npm install --save prop-types // runtime type checking for React props and similar objects
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```
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// notes: don't forget the command lines
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/* *******************************************************************************************
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* REACT
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* https://reactjs.org/docs/react-api.html
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* ******************************************************************************************* */
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// Create and return a new React element of the given type.
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// Code written with JSX will be converted to use React.createElement().
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// You will not typically invoke React.createElement() directly if you are using JSX.
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React.createElement(
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type,
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[props],
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[...children]
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)
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// Clone and return a new React element using element as the starting point.
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// The resulting element will have the original element’s props with the new props merged in shallowly.
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React.cloneElement(
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element,
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[props],
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[...children]
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)
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// Verifies the object is a React element. Returns true or false.
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React.isValidElement(object)
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React.Children // provides utilities for dealing with the this.props.children opaque data structure.
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// Invokes a function on every immediate child contained within children with this set to thisArg.
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React.Children.map(children, function[(thisArg)])
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// Like React.Children.map() but does not return an array.
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React.Children.forEach(children, function[(thisArg)])
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// Returns the total number of components in children,
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// equal to the number of times that a callback passed to map or forEach would be invoked.
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React.Children.count(children)
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// Verifies that children has only one child (a React element) and returns it.
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// Otherwise this method throws an error.
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React.Children.only(children)
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// Returns the children opaque data structure as a flat array with keys assigned to each child.
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// Useful if you want to manipulate collections of children in your render methods,
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// especially if you want to reorder or slice this.props.children before passing it down.
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React.Children.toArray(children)
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// The React.Fragment component lets you return multiple elements in a render() method without creating an additional DOM element
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// You can also use it with the shorthand <></> syntax.
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React.Fragment
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/* *******************************************************************************************
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* REACT.COMPONENT
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* React.Component is an abstract base class, so it rarely makes sense to refer to React.Component
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* directly. Instead, you will typically subclass it, and define at least a render() method.
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* https://reactjs.org/docs/react-component.html
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* ******************************************************************************************* */
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class Component extends React.Component {
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// Will be called before it is mounted
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constructor(props) {
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// Call this method before any other statement
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// or this.props will be undefined in the constructor
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super(props);
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// The constructor is also often used to bind event handlers to the class instance.
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// Binding makes sure the method has access to component attributes like this.props and this.state
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this.method = this.method.bind(this);
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// The constructor is the right place to initialize state.
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this.state = {
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active: true,
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// In rare cases, it’s okay to initialize state based on props.
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// This effectively “forks” the props and sets the state with the initial props.
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// If you “fork” props by using them for state, you might also want to implement componentWillReceiveProps(nextProps)
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// to keep the state up-to-date with them. But lifting state up is often easier and less bug-prone.
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color: props.initialColor
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};
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}
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// Enqueues changes to the component state and
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// tells React that this component and its children need to be re-rendered with the updated state.
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// setState() does not always immediately update the component. It may batch or defer the update until later.
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// This makes reading this.state right after calling setState() a potential pitfall.
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// Instead, use componentDidUpdate or a setState callback.
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// You may optionally pass an object as the first argument to setState() instead of a function.
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setState(updater[, callback]) { }
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// Invoked just before mounting occurs (before render())
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// This is the only lifecycle hook called on server rendering.
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componentWillMount() { }
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// Invoked immediately after a component is mounted.
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// Initialization that requires DOM nodes should go here.
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// If you need to load data from a remote endpoint, this is a good place to instantiate the network request.
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// This method is a good place to set up any subscriptions. If you do that, don’t forget to unsubscribe in componentWillUnmount().
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componentDidMount() { }
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// Invoked before a mounted component receives new props.
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// If you need to update the state in response to prop changes (for example, to reset it),
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// you may compare this.props and nextProps and perform state transitions using this.setState() in this method.
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componentWillReceiveProps(nextProps) { }
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// Let React know if a component’s output is not affected by the current change in state or props.
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// 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.
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// shouldComponentUpdate() is invoked before rendering when new props or state are being received. Defaults to true.
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// This method is not called for the initial render or when forceUpdate() is used.
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// Returning false does not prevent child components from re-rendering when their state changes.
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shouldComponentUpdate(nextProps, nextState) { }
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// Invoked just before rendering when new props or state are being received.
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// Use this as an opportunity to perform preparation before an update occurs. This method is not called for the initial render.
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// Note that you cannot call this.setState() here; nor should you do anything else
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// (e.g. dispatch a Redux action) that would trigger an update to a React component before componentWillUpdate() returns.
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// If you need to update state in response to props changes, use componentWillReceiveProps() instead.
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componentWillUpdate(nextProps, nextState) { }
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// Invoked immediately after updating occurs. This method is not called for the initial render.
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// Use this as an opportunity to operate on the DOM when the component has been updated.
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// 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).
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componentDidUpdate(prevProps, prevState) { }
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// Invoked immediately before a component is unmounted and destroyed.
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// Perform any necessary cleanup in this method, such as invalidating timers, canceling network requests,
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// or cleaning up any subscriptions that were created in componentDidMount().
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componentWillUnmount() { }
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// Error boundaries are React components that catch JavaScript errors anywhere in their child component tree,
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// log those errors, and display a fallback UI instead of the component tree that crashed.
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// Error boundaries catch errors during rendering, in lifecycle methods, and in constructors of the whole tree below them.
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componentDidCatch() { }
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// This method is required.
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// It should be pure, meaning that it does not modify component state,
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// it returns the same result each time it’s invoked, and
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// it does not directly interact with the browser (use lifecycle methods for this)
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// It must return one of the following types: react elements, string and numbers, portals, null or booleans.
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render() {
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// Contains the props that were defined by the caller of this component.
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console.log(this.props);
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// Contains data specific to this component that may change over time.
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// The state is user-defined, and it should be a plain JavaScript object.
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// If you don’t use it in render(), it shouldn’t be in the state.
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// For example, you can put timer IDs directly on the instance.
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// Never mutate this.state directly, as calling setState() afterwards may replace the mutation you made.
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// Treat this.state as if it were immutable.
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console.log(this.state);
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return (
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<div>
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{/* Comment goes here */}
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Hello, {this.props.name}!
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</div>
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);
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}
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}
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// Can be defined as a property on the component class itself, to set the default props for the class.
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// This is used for undefined props, but not for null props.
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Component.defaultProps = {
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color: 'blue'
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};
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component = new Component();
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// By default, when your component’s state or props change, your component will re-render.
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// If your render() method depends on some other data, you can tell React that the component needs re-rendering by calling forceUpdate().
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// Normally you should try to avoid all uses of forceUpdate() and only read from this.props and this.state in render().
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component.forceUpdate(callback)
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/* *******************************************************************************************
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* REACT.DOM
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* The react-dom package provides DOM-specific methods that can be used at the top level of
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* your app and as an escape hatch to get outside of the React model if you need to.
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* Most of your components should not need to use this module.
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* https://reactjs.org/docs/react-dom.html
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* ******************************************************************************************* */
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// Render a React element into the DOM in the supplied container and return a reference
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// to the component (or returns null for stateless components).
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ReactDOM.render(element, container[, callback])
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// Same as render(), but is used to hydrate a container whose HTML contents were rendered
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// by ReactDOMServer. React will attempt to attach event listeners to the existing markup.
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ReactDOM.hydrate(element, container[, callback])
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// Remove a mounted React component from the DOM and clean up its event handlers and state.
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// If no component was mounted in the container, calling this function does nothing.
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// Returns true if a component was unmounted and false if there was no component to unmount.
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ReactDOM.unmountComponentAtNode(container)
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// If this component has been mounted into the DOM, this returns the corresponding native browser
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// DOM element. This method is useful for reading values out of the DOM, such as form field values
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// and performing DOM measurements. In most cases, you can attach a ref to the DOM node and avoid
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// using findDOMNode at all.
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ReactDOM.findDOMNode(component)
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// Creates a portal. Portals provide a way to render children into a DOM node that exists outside
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// the hierarchy of the DOM component.
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ReactDOM.createPortal(child, container)
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/* *******************************************************************************************
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* REACTDOMSERVER
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* The ReactDOMServer object enables you to render components to static markup.
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* https://reactjs.org/docs/react-dom.html
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* ******************************************************************************************* */
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// Render a React element to its initial HTML. React will return an HTML string.
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// You can use this method to generate HTML on the server and send the markup down on the initial
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// request for faster page loads and to allow search engines to crawl your pages for SEO purposes.
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ReactDOMServer.renderToString(element)
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// Similar to renderToString, except this doesn’t create extra DOM attributes that React uses
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// internally, such as data-reactroot. This is useful if you want to use React as a simple static
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// page generator, as stripping away the extra attributes can save some bytes.
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ReactDOMServer.renderToStaticMarkup(element)
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// Render a React element to its initial HTML. Returns a Readable stream that outputs an HTML string.
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// The HTML output by this stream is exactly equal to what ReactDOMServer.renderToString would return.
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// You can use this method to generate HTML on the server and send the markup down on the initial
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// request for faster page loads and to allow search engines to crawl your pages for SEO purposes.
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ReactDOMServer.renderToNodeStream(element)
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// Similar to renderToNodeStream, except this doesn’t create extra DOM attributes that React uses
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// internally, such as data-reactroot. This is useful if you want to use React as a simple static
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// page generator, as stripping away the extra attributes can save some bytes.
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ReactDOMServer.renderToStaticNodeStream(element)
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/* *******************************************************************************************
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* TYPECHECKING WITH PROPTYPES
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* https://reactjs.org/docs/typechecking-with-proptypes.html
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* ******************************************************************************************* */
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import PropTypes from 'prop-types';
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MyComponent.propTypes = {
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// You can declare that a prop is a specific JS type. By default, these
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// are all optional.
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optionalArray: PropTypes.array,
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optionalBool: PropTypes.bool,
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optionalFunc: PropTypes.func,
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optionalNumber: PropTypes.number,
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optionalObject: PropTypes.object,
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optionalString: PropTypes.string,
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optionalSymbol: PropTypes.symbol,
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// Anything that can be rendered: numbers, strings, elements or an array
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// (or fragment) containing these types.
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optionalNode: PropTypes.node,
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// A React element.
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optionalElement: PropTypes.element,
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// You can also declare that a prop is an instance of a class. This uses
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// JS's instanceof operator.
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optionalMessage: PropTypes.instanceOf(Message),
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// You can ensure that your prop is limited to specific values by treating
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// it as an enum.
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optionalEnum: PropTypes.oneOf(['News', 'Photos']),
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// An object that could be one of many types
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optionalUnion: PropTypes.oneOfType([
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PropTypes.string,
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PropTypes.number,
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PropTypes.instanceOf(Message)
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]),
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// An array of a certain type
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optionalArrayOf: PropTypes.arrayOf(PropTypes.number),
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// An object with property values of a certain type
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optionalObjectOf: PropTypes.objectOf(PropTypes.number),
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// An object taking on a particular shape
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optionalObjectWithShape: PropTypes.shape({
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color: PropTypes.string,
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fontSize: PropTypes.number
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}),
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// You can chain any of the above with `isRequired` to make sure a warning
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// is shown if the prop isn't provided.
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requiredFunc: PropTypes.func.isRequired,
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// A value of any data type
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requiredAny: PropTypes.any.isRequired,
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// You can also specify a custom validator. It should return an Error
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// object if the validation fails. Don't `console.warn` or throw, as this
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// won't work inside `oneOfType`.
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customProp: function(props, propName, componentName) {
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if (!/matchme/.test(props[propName])) {
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return new Error(
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'Invalid prop `' + propName + '` supplied to' +
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' `' + componentName + '`. Validation failed.'
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);
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}
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},
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// You can also supply a custom validator to `arrayOf` and `objectOf`.
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// It should return an Error object if the validation fails. The validator
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// will be called for each key in the array or object. The first two
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// arguments of the validator are the array or object itself, and the
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// current item's key.
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customArrayProp: PropTypes.arrayOf(function(propValue, key, componentName, location, propFullName) {
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if (!/matchme/.test(propValue[key])) {
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return new Error(
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'Invalid prop `' + propFullName + '` supplied to' +
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' `' + componentName + '`. Validation failed.'
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);
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}
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})
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};
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