react表单

import React from ‘react‘

class Form extends React.Component {
    constructor(props) {
        super(props);
        this.state = { 
            username:‘‘,
            selectValue:‘‘,
            content:‘‘
        }
    }
    render() { 
        return (
            <div style={{padding:"10px"}}>
                <form onSubmit={this.handleSubmit}>
                    <section style={{marginBottom:"10px"}}>
                        <label htmlFor="username">姓名：</label>
                        <input type="text" id="username" value={this.state.username} 
onChange={this.changeHandle}
                    />
                    </section>
                    <section style={{marginBottom:"10px"}}>
                        <label>水果：</label>
                        <select value={this.state.selectValue} onChange={this.selectChange}>
                            <option value="grapefruit">葡萄柚</option>
                            <option value="lime">酸橙</option>
                            <option value="coconut">椰子</option>
                            <option value="mango">芒果</option>
                        </select>
                    </section>
                    <section style={{marginBottom:"10px"}}> 
                        <label style={{verticalAlign:"top"}}>内容:</label>
                        <textarea value={this.state.content} onChange={this.contentChange} />
                    </section>
                    <input type="submit" value="提交"/>
                </form>
            </div>
        );
    }
    handleSubmit=(e)=>{
        e.preventDefault();
        console.log(this.state.username);
        console.log(this.state.selectValue);
        console.log(this.state.content)
        console.log(e);
    }
    changeHandle=(e)=>{
        //用户名
        e.persist();
        this.setState({
            username:e.target.value
        })
    }
    selectChange=(e)=>{
        //水果
        e.persist();
        this.setState({
            selectValue:e.target.value
        })
    }
    contentChange=(e)=>{
        e.persist();//这个是浏览器报错提示说加的，如果需要异步访问事件属性，应在事件上调用 event.persist()
，这种操作将从事件池中删除 SyncthesicEvent，并允许用户代码保留对事件的引用。
        //内容
        this.setState({
            content:e.target.value
        })
    }
}
 
export default Form;

import React from ‘react‘
class NameForm extends React.Component {
    constructor(props) {
      super(props);
      this.username = React.createRef();
      this.password = React.createRef();
    }
    render() {
      return (
        <form onSubmit={this.handleSubmit}>
          <label>
            Name:
            <input type="text" ref={this.username} />
          </label>
          <label>
            password:
            <input type="text" ref={this.password} />
          </label>
          <input type="submit" value="Submit" />
        </form>
      );
    }
    handleSubmit=(event)=>{
        event.preventDefault();
        console.log(this.username.current.value)
        console.log(this.password.current.value)
    }
    
}

export default NameForm;