Question

I have a jQuery code that works when I insert it inside a script tag within the body. But it doesn’t work when I insert it in the head tag or include it as a js file.

Answer 1

Judging from your description you most probably forgot to put your script into a $(document).ready function:

$(function() {
    // put your code here
});

Then you can place this wherever you want on the page (head, body, external script, …).