The code below works on a live site but I can't get it to run on the site jsfiddle . it shows me the error given below:
{
  "message": "ReferenceError: $ is not defined",
  "filename": "https://stacksnippets.net/js",
  "lineno": 108,
  "colno": 9
}
Can anyone tell me why it's not working on jsfiddle? I can't find the solution, anyone here who gave me the solution The code works as you can see when it's embedded here as snippet:
   $(document).ready(function(){
    $(window).bind('scroll', function() {
    var navHeight = $( window ).height() - 70;
    if ($(window).scrollTop() > navHeight) {
     $('nav').addClass('fixed');
    }
    else {
     $('nav').removeClass('fixed');
    }
  });
 });/*
Tutorial Name: Scroll To Top Then Fixed Navigation Effect With JQuery and CSS
https://stanhub.com/scroll-to-top-then-fixed-navigation-effect-with-jquery-and-css-free-download/
Description: Create a sticky navigation bar that remains fixed to the top after scroll
Author: Stan Kostadinov
Author URI: https://stanhub.com
Version: 1.0.0 - 11.01.2014
*/
* {margin: 0; padding: 0;}
a {text-decoration: none;}
/* This class is added on scroll */
.fixed {
 position: fixed;
 top: 0;
 height: 70px;
 z-index: 1;
}
body {
 color: #fff;
 font-family: 'open-sans-bold', AvenirNext-Medium, sans-serif;
 font-size: 18px;
 text-align: center;
}
/* Navigation Settings */
nav {
 position: absolute;
 bottom: 0;
 width: 100%;
 height: 70px;
 background: #fff;
}
nav li {
 display: inline-block;
 padding: 24px 10px;
}
nav li a {
 color: #757575;
 text-transform: uppercase;
}
section {
 height: 100vh;
}
/* Screens Settings */
#screen1 {
 background: #43b29d;
}
#screen1 p {
 padding-top: 200px;
}
#screen2 {
 background: #efc94d;
}
#screen3 {
 background: #e1793d;
}
@media only screen and (max-width: 520px) {
 nav li {
  padding: 24px 4px;
 }
 nav li a {
  font-size: 14px;
 }
}<section id="screen1">
 <p>Scroll down</p>
 <nav>
   <ul>
   <li><a href="#">Home</a></li>
      <li><a href="#">About</a></li>
      <li><a href="#">Services</a></li>
      <li><a href="#">Team</a></li>
      <li><a href="#">Contact</a></li>
   </ul>
 </nav>
</section>
<section id="screen2"></section>
<section id="screen3"></section> 
     
     
     
    