Cache your React event listeners to improve performance.

some-component.js

class SomeComponent extends React.PureComponent {

  // Each instance of SomeComponent has a cache of click handlers
  // that are unique to it.
  clickHandlers = {};

  // Generate and/or return a click handler,
  // given a unique identifier.
  getClickHandler(key) {

    // If no click handler exists for this unique identifier, create one.
    if (!Object.prototype.hasOwnProperty.call(this.clickHandlers, key)) {
      this.clickHandlers[key] = () => alert(key);
    }
    return this.clickHandlers[key];
  }

  render() {
    return (
      <ul>
        {this.props.list.map(listItem =>
          <li key={listItem.text}>
            <Button onClick={this.getClickHandler(listItem.text)} />
          </li>
        )}
      </ul>
    );
  }
}