如何使用 react ref 从 html select 元素中获取值？

Question

I have a form in which I am using html select element.

  <select className="form-control" id="ntype" required >
      <option value = "">None</option>
      <option value = "1">1</option>
      <option value = "2">2</option>
      <option value = "3">3</option>
  </select>

I know with html input type element we can attach ref like below code

ref = {(input) => { this.nHeading = input; }}

and

<input
    type        = "text"
    className   = "form-control"
    id          = "tInput"
    placeholder = "Sample input"
    ref         = {(input) => { this.sInput = input; }}
    required
/>

How can I attach ref to <Select> element and get selected option value from the attached ref when form is submitted?

Do I need to attach ref to each options or select element itself?

Answer 1

You can store the value in a state on change and later use that ie make it a controlled component

 class App extends React.Component { constructor() { super(); this.state = {selectValue: ''} } callThis = (e) => { this.setState({selectValue: e.target.value}, ()=> {console.log(this.state.selectValue)}); } render() { return ( <select onChange={this.callThis}className="form-control" id="ntype" required > <option value = "">None</option> <option value = "1">1</option> <option value = "2">2</option> <option value = "3">3</option> </select> ) } } ReactDOM.render(<App/>, document.getElementById('app')); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script> <div id="app"></div> 

Or you can use refs to get the value like this

 class App extends React.Component { constructor() { super(); this.state = {selectValue: ''} } callThis = (e) => { console.log(this.selectVal.value) } render() { return ( <div><select ref={(input) => this.selectVal = input} className="form-control" id="ntype" required > <option value = "">None</option> <option value = "1">1</option> <option value = "2">2</option> <option value = "3">3</option> </select> <input type="button" value="click" onClick={this.callThis}/></div> ) } } ReactDOM.render(<App/>, document.getElementById('app')); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script> <div id="app"></div> 

Answer 2

I would give each element a value and onChange handler for the select element like this

<select className="form-control"onChange={this.onChange.bind(this)}>
    <option value="">None</option>
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
</select>

And define an onChange handler that sets the state of the selection

onChange(e){
    this.setState({value: e.target.value}, function(){

    // do other stuff

});

}

Answer 3

If you are using React functional components, you can do the following.

import { useState, useRef } from 'react';

...

  const selectRef = useRef(null)
  <select className="form-control" id="ntype" required ref={selectRef}>
      <option value = "">None</option>
      <option value = "1">1</option>
      <option value = "2">2</option>
      <option value = "3">3</option>
  </select>

then you can access the value in your submit logic by,

selectRef.current.value

Answer 4

You can just use an onChange function to set the value of the Ref. Eg:

<select className="form-control" id="ntype" required onChange={e => {yourRef.current = e.target.value}} >
      <option value = "">None</option>
      <option value = "1">1</option>
      <option value = "2">2</option>
      <option value = "3">3</option>
  </select>