Handling Multiple Inputs<\/strong><\/p>\nWhen you need to handle multiple controlled input elements, you can add a name attribute to each element and let the handler function choose what to do based on the value of event.target.name.<\/p>\n
For example:<\/p>\n
class Reservation extends React.Component {<\/p>\n
constructor(props) {<\/p>\n
super(props);<\/p>\n
this.state = {<\/p>\n
isGoing: true,<\/p>\n
numberOfGuests: 2<\/p>\n
};<\/p>\n
this.handleInputChange = this.handleInputChange.bind(this);<\/p>\n
}<\/p>\n
handleInputChange(event) {<\/p>\n
const target = event.target;<\/p>\n
const value = target.type === ‘checkbox’ ? target.checked : target.value;<\/p>\n
const name = target.name;<\/p>\n
this.setState({<\/p>\n[name]: value<\/p>\n
});<\/p>\n
}<\/p>\n
render() {<\/p>\n
return (<\/p>\n
<form><\/p>\n
<label><\/p>\n
Is going:<\/p>\n
<input<\/p>\n
name=”isGoing”<\/p>\n
type=”checkbox”<\/p>\n
checked={this.state.isGoing}<\/p>\n
onChange={this.handleInputChange} \/><\/p>\n
<\/label><\/p>\n
<br \/><\/p>\n
<label><\/p>\n
Number of guests:<\/p>\n
<input<\/p>\n
name=”numberOfGuests”<\/p>\n
type=”number”<\/p>\n
value={this.state.numberOfGuests}<\/p>\n
onChange={this.handleInputChange} \/><\/p>\n
<\/label><\/p>\n
<\/form><\/p>\n
);<\/p>\n
}<\/p>\n
}<\/p>\n
Note how we used the ES6 computed property name syntax to update the state key corresponding to the given input name:<\/p>\n
this.setState({<\/p>\n[name]: value<\/p>\n
});<\/p>\n
It is equivalent to this ES5 code:<\/p>\n
var partialState = {};<\/p>\n
partialState[name] = value;<\/p>\n
this.setState(partialState);<\/p>\n
Also, since setState() automatically merges a partial state into the current state, we only needed to call it with the changed parts.<\/p>\n
Controlled Input Null Value<\/strong><\/p>\nSpecifying the value prop on a controlled component prevents the user from changing the input unless you desire so. If you\u2019ve specified a value but the input is still editable, you may have accidentally set value to undefined or null.<\/p>\n
The following code demonstrates this. (The input is locked at first but becomes editable after a short delay.)<\/p>\n
ReactDOM.render(<input value=”hi” \/>, mountNode);<\/p>\n
setTimeout(function() {<\/p>\n
ReactDOM.render(<input value={null} \/>, mountNode);<\/p>\n
}, 1000);<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
In HTML, an <input type=”file”> lets the user choose one or more files from their device storage to be uploaded to a server or manipulated by JavaScript via the File API. <input type=”file” \/> Because its value is read-only, it is an uncontrolled component in React. It is discussed together with other uncontrolled components later…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"categories":[8528],"tags":[8595],"class_list":["post-74347","page","type-page","status-publish","hentry","category-reactjs","tag-reactjs-and-file-input-tag"],"acf":[],"yoast_head":"\n
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