In JavaScript, the preventDefault() method can be used to prevent the default behavior of an event from being triggered. This is useful in situations where we want to handle the event in a custom way, rather than allowing the default behavior to occur.

For example, if a user clicks on a link on a webpage, the default behavior is for the browser to navigate to the link’s destination. If we want to prevent this behavior and handle the click event in a custom way, we can use the preventDefault() method.

Here is an example of using preventDefault() in JavaScript:

// Select the link element on the page
var link = document.querySelector('a');

// Add a click event listener to the link
link.addEventListener('click', function(event) {
  // Prevent the default behavior of the event (navigating to the link's destination)
  event.preventDefault();

  // Handle the event in a custom way
  console.log('Link clicked, but default behavior prevented');
});

In this example, we are adding a click event listener to the link element on the page. When the user clicks on the link, the event listener is triggered and the preventDefault() method is called, which prevents the default behavior of navigating to the link’s destination. This allows us to handle the event in a custom way.

I hope this helps! Let me know if you have any questions.