load options of a select box dynamically based on value of another select box in react

Question

I m trying to create 2 select boxes in which options of 1st select box are fixed but the second ones change based on the selected value of first div.

eg: 1st Select:

<select>
    <option>Integers</option>
    <option>Alphabets</option>
</select>

Then if Integers is selected in 1st select then I want integers 1 to 10 as options in the 2nd select box. But if Alphabets is selected the a to z should come in options of the second select box.

Answer 1

You can create a lookup table object that holds both integers and Alphabets with each has a relevant key.
Then in one select you update the state with selected key and in the other select you render the options correspond to the selected key.

---

Here is a running example:

const lookup = {
  "int": [
    { id: '1', text: '1' },
    { id: '2', text: '2' },
    { id: '3', text: '3' },
    { id: '4', text: '4' },
    { id: '5', text: '5' }
  ],
  "abc": [
    { id: 'a', text: 'a' },
    { id: 'b', text: 'b' },
    { id: 'c', text: 'c' },
    { id: 'd', text: 'd' },
    { id: 'e', text: 'e' }
  ]
}

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      dataValue: 'int'
    }
  }

  onChange = ({ target: { value } }) => {
    this.setState({ dataValue: value });
  }

  render() {
    const { dataValue } = this.state;
    const options = lookup[dataValue];
    return (
      <div>
        <select onChange={this.onChange}>
          <option value="int">Integers</option>
          <option value="abc">Alphabets</option>
        </select>
        <hr />
        <select>
          {options.map(o => <option key={o.id} value={o.id}>{o.text}</option>)}
        </select>
      </div>
    );
  }
}

ReactDOM.render(<App />, document.getElementById('root'));

<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="root"></div>