Code:
input:
Why does event.target get it correctly for the determination below null,
Code:
input:
Why does event.target get it correctly for the determination below null,
this is because the events in React are not real DOM events, but rather composite events encapsulated on native DOM events.
Composite events are managed by the event pool, the composite event object may be reused, and all properties of the composite event are emptied. So when accessing the properties of a composite event in an asynchronous handler (such as setTimeout, etc.) or in the browser console, it may be empty.
the solution given in the answer above: event.persist (), simply removes the current composite event from the event pool, so you can continue to have a reference to the event and still have access to the event's properties.
event is only the current object
default react sets all its properties to null
function(e){
e.persist()
console.log(e);
}1. Write the landing page with react, after calling the background data with axios, judge the route of the page to jump according to the return value, how to jump? 2.axios.get ( login login.action?username= +name+ &password= +pd, {) timeout: 1000...
setting in state: this.state = {checkList: []}; checkList initializes it with an array of the same length as JsonPage: this.setState ({checkList:checkSaveCount}); checkSavaCount is the same length as the following JsonPage. the following creates...
import React from react ; class PublicScreen extends React.Component { constructor(props) { super(props); this.getStyle = this.getStyle.bind(this); } getStyle() { const { width = 1920, height = 1080 } = this.pr...
renderdphtmldvareturnapiBackend: apiBackend ...
react projects cannot save store? using redux, data index.js ReactDOM.render( <Provider store={store}> <Router > < Provider>, document.getElementById( root )) registerServiceWorker() actions export const SET_USER = ...
this method is included in the constructor of most components, so what exactly is this method for constructor(props,context){ super(props,context) } ...
use the Table component of Antd Design, first check out the data, and then select a CheckBox, but when you change pages, that CheckBox will not disappear. For example, when I select the first line on the first page, and then skip to the second page, the ...
I can run before packaging without any error reports. This problem occurs after packaging. reports such an error in the browser, using scaffolding made by create-react-app, and the back end is Node.js, backend. No error is reported: packages two diff...
segmentfault dvaws.open().websocketwebsocketws ws.openfetchGETloginsendfetchCOOKIECOOKIEFETCHCOOKIECOOKIE ...
...
now we need to develop a website to generate front-end pages based on the node ID saved in the database. For example, the json data is: let data=[ {"id":1,"pid":0,"type":"div"}, {"id":2,"pi...
I pass values through redux scenario is when I click on the navigation bar of component 1 and refresh the ajax of component 2 is the data returned by ajax accepted by this.state.contnet what should I write? There is an urgent need for ideas. ...
official example of full copy: this is the official sample code: import { Select } from antd ; const Option = Select.Option; function handleChange(value) { console.log(`selected ${value}`); } ReactDOM.render( <div> <Select defaul...
how to use react to change the value of Input < hr > export default class myForm extends Component{ constructor(props){ super(props); this.state = { id: , }; } change=()=>{ var idIn...
want to set the meta tag to solve the adaptive problem <meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no"> meta LOGO ...
use list as the option data source for Select, but use callback, which cannot be rendered. Just call it directly, as shown in the figure below. The first method is fine, and the second is not. Because there are many Select, on a page, you need to use th...
< H1 > github address < H1 > error will be reported when using npm run dev const path = require( path ); const merge = require( webpack-merge ); const common = require( . webpack.common.js ); dev-server let BundleAnalyzerPlugin = require( ...
import React from react ; import ReactDOM from react-dom ; import . assets styles index.less ; import Green from . assets images green.png ; import Red from . assets images red.png ; class Circle extends React.Component { constructor...
There are two areas in the State and Lifecycle section that I don t quite understand 1. State Updates are Merged The merging is shallow, so this.setState ({comments}) leaves this.state.posts intact, but completely replaces this.state.comments. ...
like this [array [xxx], array [xxx], array [xxx].] merge all xxx in array into one array [xxx.] ...