ReactJS onClick acts as event but only if they’re used on HTML-like elements.

Button.js

import React from 'react';

export class Button extends React.Component {
  render() {
    return (
      <button onClick={this.props.onClick}>
        Click me!
      </button>
    );
  }
}

Talker.js

import React from 'react';
import ReactDOM from 'react-dom';
import { Button } from './Button';

class Talker extends React.Component {
  handleClick() {
    let speech = '';
    for (let i = 0; i < 10000; i++) {
      speech += 'blah ';
    }
    alert(speech);
  }
  
  render() {
    return <Button onClick={this.handleClick} />;
  }
}

ReactDOM.render(
  <Talker />,
  document.getElementById('app')
);

Look at Button.js. When you give a an attribute named onClick, then the name onClick has special meaning. As you’ve learned, this special onClick attribute creates an event listener, listening for clicks on the :

Now look at Talker.js. Here, when you give an attribute named onClick, then the name onClick doesn’t do anything special. The name onClick does not create an event listener when used on - it’s just an arbitrary attribute name: