[jQuery] what's the difference between document.getElementById('id') and $('#id') ?

[jQuery] what's the difference between document.getElementById('id') and $('#id') ?

I'm changing some old js I had to use jQuery.
I used to have a function like this (to select a certain text input on
a form and automatically focus on it) ... :
window.onload = function() {
self.focus();
document.getElementById("userresponse").setAttribute("autocomplete","off");
document.getElementById("userresponse").focus();
}
which worked fine ... then I replace it with this:
$(function () {
self.focus();
$("#userresponse").setAttribute("autocomplete","off");
$("#userresponse").focus();
});
which fails to select the text box. why not? I thought these were
equivalent excpet the jQuery version loads sooner?
thanks
Daniel
--
Daniel McBrearty
email : danielmcbrearty at gmail.com
www.engoi.com : the multi - language vocab trainer
BTW : 0873928131
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