how to add jquery to your code code example

Example 1: add jquery to project

Google CDN: 
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>

Example 2: add jquery in js

/* Adding the script tag to the head as suggested before */

    var head = document.getElementsByTagName('head')[0];
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = "http://code.jquery.com/jquery-2.2.1.min.js";

    // Then bind the event to the callback function.
    // There are several events for cross browser compatibility.
    script.onreadystatechange = handler;
    script.onload = handler;

    // Fire the loading
    head.appendChild(script);

    function handler(){
       console.log('jquery added :)');
    }