Sometimes one has to work with pages that are not using jQuery while most developers are used to have jQuery handy.
In such situations one can use Chrome Developer Tools console (F12) to manually add jQuery on a loaded page by running following:
var j = document.createElement('script');
j.onload = function(){ jQuery.noConflict(); };
j.src = "https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js";
document.getElementsByTagName('head')[0].appendChild(j);
Version you want might differ from above(1.12.4) you can get the link for one you need here.