The event.preventDefault() is used to prevent any default action from happening.
Let us simplify with the below example.
<html> <head> <title> My First Programme </title> <script src = "https://cdnjs.cloudflare.com/ajax/libs/JQUERY/3.3.1/jquery.min.js"> </script> </head> <body> <h1> JQuery </h1> <a href = "https://www.google.com"> Click to go to google </a> <script> $( "a" ).click(function( event ) { event.preventDefault(); }); </script> </body> </html>
So, if you see the above code. We can see that there is an <a> element,
<a href = "https://www.google.com"> Click to go to google </a>
And when we click on the above link, we are taken to https://www.google.com.
Now, if we see the JQuery statement,
$( "a" ).click(function( event ) { event.preventDefault(); });
When we click on the <a> element, the JQuery statement gets triggered.
$( "a" ).click(...);
And the anonymous function inside the click() event,
function( event ) { event.preventDefault(); }
We have used the event.preventDefault() that prevents any default actions from happening.
As in this case, the default action to click on the <a> element, to reach the site https://www.google.com.
<a href = "https://www.google.com"> Click to go to google </a>
And the event.preventDefault() stops the above action.