OnChange event using React JS for drop down
JavascriptReactjsJavascript Problem Overview
var MySelect = React.createClass({
change: function(){
return document.querySelector('#lang').value;
},
render: function(){
return(
<div>
<select id="lang">
<option value="select" onChange={this.change}>Select</option>
<option value="Java" onChange={this.change}>Java</option>
<option value="C++" onChange={this.change}>C++</option>
</select>
<p></p>
<p value={this.change}></p>
</div>
);
}
});
React.render(<MySelect />, document.body);
The onChange
event does not work.
Javascript Solutions
Solution 1 - Javascript
The change event is triggered on the <select>
element, not the <option>
element. However, that's not the only problem. The way you defined the change
function won't cause a rerender of the component. It seems like you might not have fully grasped the concept of React yet, so maybe "Thinking in React" helps.
You have to store the selected value as state and update the state when the value changes. Updating the state will trigger a rerender of the component.
var MySelect = React.createClass({
getInitialState: function() {
return {
value: 'select'
}
},
change: function(event){
this.setState({value: event.target.value});
},
render: function(){
return(
<div>
<select id="lang" onChange={this.change} value={this.state.value}>
<option value="select">Select</option>
<option value="Java">Java</option>
<option value="C++">C++</option>
</select>
<p></p>
<p>{this.state.value}</p>
</div>
);
}
});
React.render(<MySelect />, document.body);
Also note that <p>
elements don't have a value
attribute. React/JSX simply replicates the well-known HTML syntax, it doesn't introduce custom attributes (with the exception of key
and ref
). If you want the selected value to be the content of the <p>
element then simply put inside of it, like you would do with any static content.
Learn more about event handling, state and form controls:
Solution 2 - Javascript
React Hooks (16.8+):
const Dropdown = ({
options
}) => {
const [selectedOption, setSelectedOption] = useState(options[0].value);
return (
<select
value={selectedOption}
onChange={e => setSelectedOption(e.target.value)}>
{options.map(o => (
<option key={o.value} value={o.value}>{o.label}</option>
))}
</select>
);
};
Solution 3 - Javascript
import React, { PureComponent, Fragment } from 'react';
import ReactDOM from 'react-dom';
class Select extends PureComponent {
state = {
options: [
{
name: 'Select…',
value: null,
},
{
name: 'A',
value: 'a',
},
{
name: 'B',
value: 'b',
},
{
name: 'C',
value: 'c',
},
],
value: '?',
};
handleChange = (event) => {
this.setState({ value: event.target.value });
};
render() {
const { options, value } = this.state;
return (
<Fragment>
<select onChange={this.handleChange} value={value}>
{options.map(item => (
<option key={item.value} value={item.value}>
{item.name}
</option>
))}
</select>
<h1>Favorite letter: {value}</h1>
</Fragment>
);
}
}
ReactDOM.render(<Select />, window.document.body);
Solution 4 - Javascript
handleChange(value, selectOptionSetter) => {
selectOptionSetter(value)
// handle other stuff like persisting to store etc
}
const Dropdown = (props) => {
const { options } = props;
const [selectedOption, setSelectedOption] = useState(options[0].value);
return (
<select
value={selectedOption}
onChange={e => handleChange(e.target.value, setSelectedOption)}>
{options.map(o => (
<option key={o.value} value={o.value}>{o.label}</option>
))}
</select>
);
};
Solution 5 - Javascript
If you are using select as inline to other component, then you can also use like given below.
<select onChange={(val) => this.handlePeriodChange(val.target.value)} className="btn btn-sm btn-outline-secondary dropdown-toggle">
<option value="TODAY">Today</option>
<option value="THIS_WEEK" >This Week</option>
<option value="THIS_MONTH">This Month</option>
<option value="THIS_YEAR">This Year</option>
<option selected value="LAST_AVAILABLE_DAY">Last Availabe NAV Day</option>
</select>
And on the component where select is used, define the function to handle onChange like below:
handlePeriodChange(selVal) {
this.props.handlePeriodChange(selVal);
}
Solution 6 - Javascript
I'll add this here, in case it helps someone because this was the solution that helped me.
This is to get the SELECTED INDEX. Not for the value. (Worked for me because my options list was a list of numbers)
const [selectedOption, setSelectedOption] = useState(0)
<select onChange={event => setSelectedOption(event.target.options.selectedIndex)}>
Solution 7 - Javascript
Thank you Felix Kling, but his answer need a little change:
var MySelect = React.createClass({
getInitialState: function() {
return {
value: 'select'
}
},
change: function(event){
this.setState({value: event.target.value});
},
render: function(){
return(
<div>
<select id="lang" onChange={this.change.bind(this)} value={this.state.value}>
<option value="select">Select</option>
<option value="Java">Java</option>
<option value="C++">C++</option>
</select>
<p></p>
<p>{this.state.value}</p>
</div>
);
}
});
React.render(<MySelect />, document.body);
Solution 8 - Javascript
var MySelect = React.createClass({
getInitialState: function() {
var MySelect = React.createClass({
getInitialState: function() {
return {
value: 'select'
}
},
change: function(event){
event.persist(); //THE MAIN LINE THAT WILL SET THE VALUE
this.setState({value: event.target.value});
},
render: function(){
return(
<div>
<select id="lang" onChange={this.change.bind(this)} value={this.state.value}>
<option value="select">Select</option>
<option value="Java">Java</option>
<option value="C++">C++</option>
</select>
<p></p>
<p>{this.state.value}</p>
</div>
);
}
});
React.render(<MySelect />, document.body);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>