您需要與controlled input
爲了提供一個值選項字段像
handleChange(e) {
var whoIsChecked = {...this.state.whoIsChecked}
whoIsChecked.allowDestroyAll = e.target.value
this.setState({whoIsChecked})
}
render() {
return <select
className="form-control"
id="ada"
onChange={(e) => this.handleChange(e)}
value={this.state.whoIsChecked.allowDestroyAll}>
<option value="true">true</option>
<option value="false">false</option>
</select>
}
後更改值添加
onChange
事件和更新狀態
class App extends React.Component {
state= {
whoIsChecked: {
allowDestroyAll: "true"
}
}
handleChange(e) {
var whoIsChecked = {...this.state.whoIsChecked}
whoIsChecked.allowDestroyAll = e.target.value
this.setState({whoIsChecked},()=> {console.log(this.state)})
}
render() {
return <select
className="form-control"
id="ada"
onChange={(e) => this.handleChange(e)}
value={this.state.whoIsChecked.allowDestroyAll}>
<option value="true">true</option>
<option value="false">false</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>
這非常含糊。請嘗試提供更多的上下文。 –
這已在不同的主題上得到解答。請看看https://stackoverflow.com/questions/29108779/how-to-get-selected-value-of-a-dropdown-menu-in-reactjs –
可能的重複[如何獲取下拉菜單的選定值在ReactJS](https://stackoverflow.com/questions/29108779/how-to-get-selected-value-of-a-dropdown-menu-in-reactjs) – GrumpyCrouton