You Don't Need JQuery
You can basically sum up this entire rather ridiculous site with "Yes, you don't need jQuery, you can just use the built-in methods, but using jQuery is generally more pleasant, more consistent, and involves less typing".  One particularly egregious example from the site:  $('#foo').removeClass('bold');

vs.  document.getElementById('foo').className = 
      document.getElementById('foo').className.replace(/^bold$/, '');

The author summarises this, helpfully: "As usual, more characters, but still easy without jQuery."Of course, if you were doing that remove class operation quite often, rather than writing all that code out each time, you might wrap it up in a helper method, and maybe you'd call it, I don't know, "removeClass" or something; perhaps if you were doing a whole bunch of DOM operations you might create little helper methods for each one, again to save you some typing.  Pretty quickly you might end up with a little library of helper methods... and, of course, being a wonderful programmer who never makes mistakes, I'm sure that little library would be every bit as optimised, reliable, and correct as a battle-tested library used on hundreds of thousands of web sites.