ref useRef React.createRef React.forwardRef

react如何获取真实DOM:useRef, React.CreateRef()

access DOM nodes directly within React:ref.current

Let's say you want to change the value of an <input> element, but without using props or re-rendering the whole component. They're an excellent way to update part of a component without the need to re-render the entire thing.


  1. useRef

const {useRef} = React

const App=()=>{

const buttonRef=useRef();

return(

<button

onClick={()=>{console.log(buttonRef.current);}}

ref={buttonRef} >

Special Button

</button>

);

}


  1. React.createRef()

create a ref by calling React.createRef() and attaching a React element to it using the ref attribute on the element.

class Example extends React.Component {

constructor(props) {

super(props)

this.exampleRef = React.createRef() // Create the ref

}

render() {

return (

<div>

//这里是uncontrolled form

<input type="text" ref={this.exampleRef} /> // Call the ref with the `ref` attribute

</div>

)

}}


  1. Passing a callback function to ref

create a ref by passing a callback function to the ref attribute of a component.

<input type="text" ref={element=>this.textInput=element}/>

The callback is used to store a reference to the DOM node in an instance property. When we want to make use of this reference, we access it using: this.textInput.value

When you make use of callback like we did above, React will call the ref callback with the DOM node when the component mounts, when the component un-mounts, it will call it with null.

class App extends React.Component {

state = { value: '' }

handleSubmit = e => {

e.preventDefault();

this.setState({ value: this.textInput.value})

};

render() {

return (

<div>

<h3>Value: {this.state.value}</h3>

<form onSubmit={this.handleSubmit}>

<input type="text" ref={element => this.textInput = element} />

<button>Submit</button>

</form>

</div>

); }}


  1. pass ref from a parent component to a child component using callbacks.

child:

const Input = props =>{

return(

//This component is expecting inputRef props from its parent component which is then used to create a ref to the DOM node.

<inputtype="text" ref={ props.inputRef }/>

);

};

parent:

In the App component, we want to obtain the text that is entered in the input field (which is in the child component) so we can render it. The ref is created using a callback like we did in the first example of this section. The key lies in how we access the DOM of the input element in the Input component from the App component. If you look closely, we access it using this.inputElement. So, when updating the state of value in the App component, we get the text that was entered in the input field using this.inputElement.value.

class App extends React.Component{

state={

value:""

};

handleSubmit=event=>{

this.setState({ value:this.inputElement.value });

};

render() {

return(

<div>

<h3>Value: {this.state.value}</h3>

<Input inputRef={el=>(this.inputElement=el)}/>

<button onClick={this.handleSubmit}>Submit</button>

</div>

);}}


  1. Forwarding a ref from one component to another

Ref forwarding is the technique of passing a ref from a component to a child component by making use of the React.forwardRef() method.

child:

const Input=React.forwardRef((props,ref)=>(

<inputtype="text"ref={ref}/>

));

parent:

class App extends React.Component{

constructor(props) {

super(props)

this.inputRef=React.createRef();

this.state={value:''}

}

handleSubmit=e=>{

e.preventDefault();

this.setState({value:this.inputRef.current.value})

};

render() {

return(

<div>

<h3>Value: {this.state.value}</h3>

<form onSubmit={this.handleSubmit}>

<Input ref={this.inputRef}/>

<button>Submit</button>

</form>

</div>

);}}


uncontrolled form example: Using ref for form validation

class App extends React.Component {

constructor(props) {

super(props);

this.username = React.createRef();

this.password = React.createRef();

this.state = {

errors: []

};

}

handleSubmit = (event) => {

event.preventDefault();

const username = this.username.current.value;

const password = this.password.current.value;

const errors = this.handleValidation(username, password);

if (errors.length > 0) {

this.setState({ errors });

return;

}

// Submit data

};

handleValidation = (username,password) => {

const errors = [];

if (username.length === 0) { errors.push("Username cannot be empty"); }

if (password.length < 6) { errors.push("Password should be at least 6 characters long");}

return errors;

};

render() {

const { errors } = this.state;

return (

<form onSubmit={this.handleSubmit}>

{errors.map(error => <p key={error}>{error}</p>)}

<input type="text" ref={this.username} />

<input type="text" ref={this.password} />

<button>Submit</button>

</form>

);}}


访问节点的情况

将节点绑定在this.input属性上

dom api:focus

无状态
最后编辑于:2025-01-11 21:04:55
© 著作权归作者所有,转载或内容合作请联系作者

喜欢的朋友记得点赞、收藏、关注哦!!!

相关推荐
码哥DFS1 小时前
Flex布局原理
前端·css·css3
超级小忍1 小时前
服务端向客户端主动推送数据的几种方法(Spring Boot 环境)
java·spring boot·后端
张小洛2 小时前
Spring AOP 设计解密:代理对象生成、拦截器链调度与注解适配全流程源码解析
java·后端·spring·spring aop·aop
时间会给答案scidag2 小时前
报错 400 和405解决方案
vue.js·spring boot
长路 ㅤ   2 小时前
前端技术博客汇总文档
javascript·vue.js·css3·html5·前端技术
Wyc724092 小时前
SpringBoot
java·spring boot·spring
ladymorgana4 小时前
【Spring Boot】HikariCP 连接池 YAML 配置详解
spring boot·后端·mysql·连接池·hikaricp
neoooo4 小时前
别慌,Java只有值传递——一次搞懂“为啥我改了它还不变”!
java·后端·spring
GJCTYU5 小时前
spring中@Transactional注解和事务的实战理解附代码
数据库·spring boot·后端·spring·oracle·mybatis
linweidong6 小时前
七牛云Java开发面试题及参考答案(60道面试题汇总)
spring·读写分离·aop·cap·java开发·spring ioc·java面经