这是一个如何完成此操作的最小示例，在基于值的事件处理程序中将事件处理程序添加onChange到您的第一个选择中：setState

handleChange(event) {
    let value = event.target.value;
    this.setState({
        disabled: value == '2'
    });
}
render() {
    return (
        <div>
            <select ref="selectOption" onChange={(e) => this.handleChange(e)}>
               <option selected value="1" >Option 1</option>
               <option value="2" >Option 2</option>
            </select>

            <select ref="selectTime" disabled={this.state.disabled}>
               <option value="a" >January</option>
               <option value="b" >Febreaury</option>
            </select>
        </div>
    )
}

这将是实现这一目标的反应方式：

export default class Test extends Component{

  constructor(props) {
    super(props)

    this.state = {
      selectOptionValue: '1'
    }
  }

  handleOnChange = (e) => {
    this.setState({
      selectOptionValue: e.target.value
    })
  }

  render(){
    return (
      <div>
        <select defaultValue = "1" onChange={this.handleOnChange}>
          <option value="1" >Option 1</option>
          <option value="2" >Option 2</option>
        </select>

        <select  disabled={ this.state.selectOptionValue === '2' }>
          <option value="a" >January</option>
          <option value="b" >Febreaury</option>
        </select>
      </div>
    )
  }
}

onChange从这个事件怎么样？为了您的方便：

class FlavorForm extends React.Component {
  constructor(props) {
    super(props);
    this.state = {value: 'coconut'};

    this.handleChange = this.handleChange.bind(this);
    this.handleSubmit = this.handleSubmit.bind(this);
  }

  handleChange(event) {
    this.setState({value: event.target.value});
  }

  handleSubmit(event) {
    alert('Your favorite flavor is: ' + this.state.value);
    event.preventDefault();
  }

  render() {
    return (
      <form onSubmit={this.handleSubmit}>
        <label>
          Pick your favorite La Croix flavor:
          <select value={this.state.value} onChange={this.handleChange}>
            <option value="grapefruit">Grapefruit</option>
            <option value="lime">Lime</option>
            <option value="coconut">Coconut</option>
            <option value="mango">Mango</option>
          </select>
        </label>
        <input type="submit" value="Submit" />
      </form>
    );
  }
}

这是定义需要设置哪个状态变量的另一种方法。

state = { someStateVariable : "" }

render() {
    return (
        <select onChange={event => this._setSelected({ someStateVariable: event.target.value })}>
            <option value="1">One</option>
            ...
        </select>
    );
}

_setSelected = newState => {
    this.setState(newState)
}

如果您想保持简单并使用纯 JavaScript，则可以使用以下代码段。

document.querySelector('select[ref="selectOption"]').addEventListener('change', function(e) {
  document.querySelector('select[ref="selectTime"]').disabled = (e.target.value === '2') ? true : false;
})

<select ref="selectOption">
  <option selected value="1">Option 1</option>
  <option value="2">Option 2</option>
</select>

<select ref="selectTime">
  <option value="a">January</option>
  <option value="b">Febreaury</option>
</select>

第 1 步 - 创建状态并将初始值设置为空字符串

      const [category,setCategory] = useState('');

第 2 步映射您的选项并在选项值 === 选择值中检查 id，然后将 selected 设置为 true

  const renderedResults = results.map((result) => {
    const selected = category === result.id ? "true" : '';
    return (
      <option selected={selected} key={result._id} value={result._id}>{result?.name}</option>
      );
  });

第 3 步

 <select
   onChange={(e) => {
    setCategory(e.target.value);
   }}
   className="form-select"
   aria-label={"Default select example"}
   >
   <option value="">Select a category</option>
     {renderedResults}
 </select>