我正在使用react-js处理简单的表单元素。
有三个组成部分:
问题是当用户将文本放入输入字段时,setState()函数无法正常工作且数据未更新。出于测试目的,当我在app js组件中放置console.log时,它在控制台上显示未定义。任何人都请这样。我想在状态更新时控制更新的数据
App.js
import React, { Component } from 'react';
import InputField from './TakeInput';
class App extends Component {
state = {
userInp : '',
outText : ''
}
handlechanger2 = (v) => {
this.setState( () => ({
userInp: v,
}))
console.log(this.userInp);
}
render() {
return (
<div className="App">
<InputField changingVal={this.handlechanger2}/>
</div>
);
}
}
export default App;
TakeInput.JS
import React, { Component } from 'react';
class TakeInput extends Component{
state={
txt: ''
}
handlerChange = (e)=>{
const { changingVal } = this.props;
const v = document.getElementById("userInput").value;
changingVal(v);
// console.log(e.target.value);
this.setState({ txt: e.target.value })
}
render(){
return(
<input type="text" name="userInput" id="userInput" placeholder="Please Enter Text" onChange={this.handlerChange} value={this.txt}/>
)
}
}
export default TakeInput;
index.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import * as serviceWorker from './serviceWorker';
ReactDOM.render(<App />, document.getElementById('root'));
serviceWorker.unregister();
这是关于你正在发展错误的方式。我认为你的文本输入应该在你的父组件
import React, { Component } from 'react';
class TakeInput extends Component{
handlerChange = (e)=>{
this.props.onChange(e.target.value);
}
render(){
return(
<input type="text" name="userInput" placeholder="Please Enter Text" onChange={this.handlerChange} value={this.props.txt}/>
)
}
}
export default TakeInput;
import React, { Component } from 'react';
import InputField from './TakeInput';
class App extends Component {
state = {
userInp : '',
outText : ''
}
handlechanger2 = (v) => {
this.setState( () => ({
userInp: v,
}))
console.log(this.state.userInp);
}
render() {
return (
<div className="App">
<InputField txt={this.state.userInp} onChange={this.handlechanger2}/>
</div>
);
}
}
export default App;
你正在尝试console.log this.userInp
。它应该是this.state.userInp
。
另外,要在最后设置状态之后立即查看更新,您可以执行以下操作:
handlechanger2 = (v) => {
this.setState( () => ({
userInp: v,
}), function(){ console.log(this.state.userInp);}) // set a callback on the setState
}