jQuery is a fast, small, and feature-rich JavaScript library. It makes things like HTML document traversal and manipulation, event handling, animation, and Ajax much simpler with an easy-to-use API that works across a multitude of browsers. With a combination of versatility and extensibility, jQuery has changed the way that millions of people write JavaScript.

http://jquery.com

Example 1) Hide all the content in <p> tag based in jQuery.

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
  $("p").click(function(){
    $(this).hide();
  });
});
</script>
</head>
<body>

<p>If you click on me, I will disappear.</p>
<p>Click me away!</p>
<p>Click me too!</p>

</body>
</html>

Example 2) Call a URL, and show its response

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script>
var fd = new FormData();    
fd.append( 'file', input.files[0] );

jQuery.ajax({
  url: 'http://example.com/script.php',
  type: 'POST',
  data: fd,
  processData: false,
  contentType: false,
  async: false,
  success: function(response){
    alert(response);
  }
});
</script>

Example 2) Call a URL, and use its Json object

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script>
var fd = new FormData();    
fd.append( 'file', input.files[0] );

jQuery.ajax({
  url: 'http://example.com/script.php',
  type: 'POST',
  data: fd,
  processData: false,
  contentType: false,
  async: false,
  success: function(response){
    var obj=JSON.parse(response);
	alert( obj.result[0].message);
  }
});
</script>