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Just like HTML DOM events, React can perform actions based on user events.

React has the same events as HTML: click, change, mouseover etc.

Adding Events

React events are written in camelCase syntax:

onClick instead of onclick.

React event handlers are written inside curly braces:

onClick={shoot}  instead of onClick="shoot()".

React:

<button onClick={shoot}>Take the Shot!</button>

HTML:

<button onclick="shoot()">Take the Shot!</button>

Example:

Put the shoot function inside the Football component:

function Football() {
  const shoot = () => {
    alert("Great Shot!");
  }

  return (
    <button onClick={shoot}>Take the shot!</button>
  );
}

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<Football />);

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Passing Arguments

To pass an argument to an event handler, use an arrow function.

Example:

Send "Goal!" as a parameter to the shoot function, using arrow function:

function Football() {
  const shoot = (a) => {
    alert(a);
  }

  return (
    <button onClick={() => shoot("Goal!")}>Take the shot!</button>
  );
}

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<Football />);

React Event Object

Event handlers have access to the React event that triggered the function.

In our example the event is the "click" event.

Example:

Arrow Function: Sending the event object manually:

function Football() {
  const shoot = (a, b) => {
    alert(b.type);
    /*
    'b' represents the React event that triggered the function,
    in this case the 'click' event
    */
  }

  return (
    <button onClick={(event) => shoot("Goal!", event)}>Take the shot!</button>
  );
}

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<Football />);

This will come in handy when we look at in a later chapter.

Test Yourself With Exercises

Exercise:

Complete this statement to include a click event handler.

<button ={clicked()}>Click Me!</button>

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