Code:
this.state={
data:[]
}
this.arr=[]this.setState({
data:this.state.data.push(ele) //push
})
this.arr.push(ele) //although push returns the length of the new array, this.arr can use push, and this.state.data can only use cancat, instead of cancat,.
in the rendering mechanism of React, directly modifying the state value cannot trigger re-rendering, but can only be performed by calling setState. This method is an asynchronous method, which puts the changes into a queue. React will merge all changes in this queue to determine whether the state has changed, thus deciding whether to re-render.
for array type state, such as data. here React states that all states contained in state should be immutable objects. This makes it easy to determine whether the state has changed-just to determine whether the reference is the same. The concat method of the array is to create a whole new array, and React thinks that state.data has changed.
setState is used to update State, and you push to update data (in fact, this is not allowed, because you can only update data with setState).
try this
this.setState({
data:[...this.state.data,ele]//setState
})this.state.data.push (ele) is the array length. Change the data data type to a number. If you execute this method again, you will get an error
even if your push is successful, it will not cause the view update. You need to return a new reference
.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 ...
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. ...
the npm start command runs normally, but the error will be reported when executing with npm run build as follows: syntax error: Unexpected token (Unexpected token (26:6) my index.js: import React, { Component } from react ; import ReactDOM from...
I want to use document.execCommand ( "copy ") to click the button to copy the link, but display TypeError: Cannot read property select of undefined Code: import React, { Component } from react import MuiThemeProvider from material-ui styles...
how to reset after selecting a value in the drop-down box this.state({ code: , codeList: , }) componentWillMount(){ init(); } <Select ref="xzSelect" defaultValue="" onSelect={val => this.set...
uses the dva framework the content of the router.js file is like this index.js ask God for guidance ...
has the following react components: import ". Home.scss"; class Home extends React.Component{ render(){ return ( <div className="box clearfix"> <div className="left"> ...
Why does test.js (lib test.js) compiled by webpack go wrong? fundamental alignment of source code import React, { Component } from react export default class Test extends Component { render() { return <h1>Test< h1> } } erase...
use the drop-down box of React s ant design, and ask for help on how to solve the problem according to the fact that there is no multiple selection in the doc, on the official website. <Select multiple showSearch onSelect={(val,e) =&g...
this is action.js reducer.js connect.js action.js the error is this.props.setSkin () is not a function, I have dispacth (setSkin ()) to props in connect, and I have also used Provider, at the top level, but still report such an error. I don t...
update the store data twice in a row, and the second time you will get the original store such as . initState ={ a: , b: }; dispatch(setState(a,1)) dispatch(setState(b,1)) the final state result is { a: , b:1 } if you repla...
when I use react antd, one of the functions is to upload pictures, but after I select the picture, the picture does not appear in my preset picture box, but runs below the preset box. here is my code this picture with an OK button is the box I pre...
when using react and antdesign as background, I need to implement this function: use the Tab component, click the label to change the route to realize the reloading of the data below, but there is always a problem when you do it. After clicking, it...
execute serve-s locally after executing npm run build locally. Transfer the build file to Ali Cloud via localhost access, and then execute serve-s in the build file. finally shows that the deployment is successful . but it cannot be accessed through ...
recently encountered a demand, the react project needs to add a rich text editor, there are many online, to find a braft-editor, their own new project to use no problem. However, when adding to the project, because the project uses server rendering (jus...
is usually the first time to visit the page, or after cleaning up the browser data, there will be a problem, there will be no problem after refreshing (click events can be used..), the path is nothing. The 50kb of the css file is about large, but the fi...
recently, I was working on a project based on a background platform of react dva and antd. I took over the project halfway. With the deepening of my work, I found that the code of pro on the official website and some logic code of our company s project ...
< H2 > react-router routing jump error using history.push < H2 > routing page http: localhost:8888 detail 5aae1cc8f5dfc27d7ad98909 Route form <Route path=" detail :id" component = {TopicDetail} key = "detail" > <Ro...
data is available. You can print renderSelect , but you can t render it below. {selectData} this cannot be rendered? Why? How to solve render(){ const {dispatch}=this.props; const selectData=this.state.selectData con...
can the file in .bundle format be decompiled or get the js file in it in some other way? solve? ...