As Aishwarya says, it does look like jQuery hasn’t loaded correctly in your browser.
There are a few things you can try to find out the problem.
Firstly, I would look in your developer tools if you use Chrome. Is there anything in your browser console log? Now look in the network tab, can you see a request for jQuery being made? There may be some network filtering such as an antispam filter blocking access.
I suspect you will find something is blocking the jQuery library from loading.
I hope this gives you some pointers and helps solve the problem.
This happens when jQuery library is not correctly loaded. Can you check that once?
perhaps $(document.body) works for you.