Test case details

Preparation Code

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script> <p id="foo">Test</p>
var $_ = function(n) {       return $(document.getElementById(n));     }

Test cases

Test #1

var a = document.getElementById('foo123');  

Test #2

var a = jQuery('#foo123');

Test #3

var a = $(document.getElementById('foo123'));

Test #4

var a = $_('foo123');