Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

OnChange event using React JS for drop down

People also ask

How do you add onChange event on dropdown in react JS?

To handle the onChange event on a select element in React: Set the onChange prop on the select element. Keep the value of the selected option in a state variable. Every time the user changes the selected option, update the state variable.

How do I change dropdown value in React?

To set selected value of a select drop down to null with React, we can set the state we use as the value of the value prop of the select drop down to null . to set onChange to a function that calls setSelected to e. target. value which is the selected value if it's truthy.

How do you handle a select dropdown in react JS?

To create a dropdown select in React, use the react-select library. The react-select library has features dynamic search/filter, async option loading, accessibility, and fast render times. In addition, it has a flexible and beautiful Select Input control for ReactJS with multi-select, autocomplete, and ajax support.


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:

  • http://facebook.github.io/react/docs/interactivity-and-dynamic-uis.html
  • http://facebook.github.io/react/docs/forms.html

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>
  );
};

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);

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);
}

  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>
  );
};