index.js

class IndexPage extends React.Component {
  _click = () => {
    console.log('clicked')
  }

  render() {
    return (
      <div>
        <p>
          <span
            style={{
              fontWeight: 'bold',
              color: 'purple',
              cursor: 'pointer',
            }}
            onClick={this._click}
          >
            Click me
          </span>
          {' to see miracle'}
        </p>
      </div>
    )
  }
}

export default IndexPage