about jquery code example

Example 1: jquery

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>

Example 2: what is jquery

jQuery is a lightweight, "write less, do more", JavaScript library.

The purpose of jQuery is to make it  much easier to use JavaScript on
your website. 

jQuery takes a lot of common tasks that require many lines of JavaScript code
to accomplish, and wraps them into methods that you can call with a single
line of code.