How to use radio buttons in ReactJS?

Here is the simplest way of implementing radio buttons in react js.

class App extends React.Component {
  
  setGender(event) {
    console.log(event.target.value);
  }
  
  render() {
    return ( 
      <div onChange={this.setGender.bind(this)}>
        <input type="radio" value="MALE" name="gender"/> Male
        <input type="radio" value="FEMALE" name="gender"/> Female
      </div>
     )
  }
}

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>

Edited

You can use arrow function instead of binding. Replace the above code as

<div onChange={event => this.setGender(event)}>

For a default value use defaultChecked, like this

<input type="radio" value="MALE" defaultChecked name="gender"/> Male

Based on what React Docs say:

Handling Multiple Inputs. When 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.

For example:

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

  handleChange = e => {
    const { name, value } = e.target;

    this.setState({
      [name]: value
    });
  };

  render() {
    return (
      <div className="radio-buttons">
        Windows
        <input
          id="windows"
          value="windows"
          name="platform"
          type="radio"
          onChange={this.handleChange}
        />
        Mac
        <input
          id="mac"
          value="mac"
          name="platform"
          type="radio"
          onChange={this.handleChange}
        />
        Linux
        <input
          id="linux"
          value="linux"
          name="platform"
          type="radio"
          onChange={this.handleChange}
        />
      </div>
    );
  }
}

Link to example: https://codesandbox.io/s/6l6v9p0qkr

At first, none of the radio buttons is selected so this.state is an empty object, but whenever the radio button is selected this.state gets a new property with the name of the input and its value. It eases then to check whether user selected any radio-button like:

const isSelected = this.state.platform ? true : false;

EDIT:

With version 16.7-alpha of React there is a proposal for something called hooks which will let you do this kind of stuff easier:

In the example below there are two groups of radio-buttons in a functional component. Still, they have controlled inputs:

function App() {
  const [platformValue, plaftormInputProps] = useRadioButtons("platform");
  const [genderValue, genderInputProps] = useRadioButtons("gender");
  return (
    <div>
      <form>
        <fieldset>
          Windows
          <input
            value="windows"
            checked={platformValue === "windows"}
            {...plaftormInputProps}
          />
          Mac
          <input
            value="mac"
            checked={platformValue === "mac"}
            {...plaftormInputProps}
          />
          Linux
          <input
            value="linux"
            checked={platformValue === "linux"}
            {...plaftormInputProps}
          />
        </fieldset>
        <fieldset>
          Male
          <input
            value="male"
            checked={genderValue === "male"}
            {...genderInputProps}
          />
          Female
          <input
            value="female"
            checked={genderValue === "female"}
            {...genderInputProps}
          />
        </fieldset>
      </form>
    </div>
  );
}

function useRadioButtons(name) {
  const [value, setState] = useState(null);

  const handleChange = e => {
    setState(e.target.value);
  };

  const inputProps = {
    name,
    type: "radio",
    onChange: handleChange
  };

  return [value, inputProps];
}

Working example: https://codesandbox.io/s/6l6v9p0qkr

Any changes to the rendering should be change via the state or props (react doc).

So here I register the event of the input, and then change the state, which will then trigger the render to show on the footer.

var SearchResult = React.createClass({
  getInitialState: function () {
    return {
      site: '',
      address: '',
    };
  },
  onSiteChanged: function (e) {
    this.setState({
      site: e.currentTarget.value,
    });
  },

  onAddressChanged: function (e) {
    this.setState({
      address: e.currentTarget.value,
    });
  },

  render: function () {
    var resultRows = this.props.data.map(function (result) {
      return (
        <tbody>
          <tr>
            <td>
              <input
                type="radio"
                name="site_name"
                value={result.SITE_NAME}
                checked={this.state.site === result.SITE_NAME}
                onChange={this.onSiteChanged}
              />
              {result.SITE_NAME}
            </td>
            <td>
              <input
                type="radio"
                name="address"
                value={result.ADDRESS}
                checked={this.state.address === result.ADDRESS}
                onChange={this.onAddressChanged}
              />
              {result.ADDRESS}
            </td>
          </tr>
        </tbody>
      );
    }, this);
    return (
      <table className="table">
        <thead>
          <tr>
            <th>Name</th>
            <th>Address</th>
          </tr>
        </thead>
        {resultRows}
        <tfoot>
          <tr>
            <td>chosen site name {this.state.site} </td>
            <td>chosen address {this.state.address} </td>
          </tr>
        </tfoot>
      </table>
    );
  },
});

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