In JavaScript, preventDefault() and stopPropagation() are two methods used to control the behavior of events, but they serve distinct purposes. Here’s a detailed explanation of their differences:

preventDefault()

Purpose:

Prevents the browser’s default action associated with an event.

Use Case:

Use preventDefault() when you want to stop the default behavior of an event, such as preventing a link from navigating, a form from submitting, or a checkbox from toggling.

Example:

Prevent a link’s default navigation:

<a href="https://example.com" id="myLink">Click Me</a>

<script>
  document.getElementById('myLink').addEventListener('click', (event) => {
    event.preventDefault(); // Prevents the browser from navigating to the URL
    console.log('Default navigation prevented.');
  });
</script>

• It does not stop the event from propagating through the DOM hierarchy (bubbling or capturing still happens).
• Commonly used for customizing behavior without affecting the event flow.

stopPropagation()

Purpose:

Stops the event from propagating (bubbling up or capturing down) through the DOM.

Use Case:

Use stopPropagation() when you want to prevent the event from reaching other event listeners attached to parent or ancestor elements.

Example:

Prevent a parent element’s event listener from being triggered:

<div id="parent">
  <button id="child">Click Me</button>
</div>

<script>
  document.getElementById('parent').addEventListener('click', () => {
    console.log('Parent clicked');
  });

  document.getElementById('child').addEventListener('click', (event) => {
    event.stopPropagation(); // Prevents the event from bubbling up to the parent
    console.log('Child clicked, propagation stopped.');
  });
</script>

• It does not prevent the default behavior of the event.
• Only stops the event from propagating to other listeners in the DOM tree.

Combining Both

Sometimes, you may need to use both methods to fully control an event:

<button id="myButton">Click Me</button>

<script>
  document.getElementById('myButton').addEventListener('click', (event) => {
    event.preventDefault();   // Prevent the default button action
    event.stopPropagation();  // Stop the event from propagating further
    console.log('Button clicked, default prevented, propagation stopped.');
  });
</script>

In this case:

• The button’s default behavior is stopped.
• The event does not bubble to any parent listeners.