Do I really need to check if an element exists with jQuery?

Question

I recently had a question about how to correctly check if an element exists with jQuery. I found the answer from here:

https://learn.jquery.com/using-jquery-core/faq

Answer 1

It matters, and $( "#myDiv" ).length is better because it is not running document.getElementById('myDiv') twice. If you were caching the selector, it would matter much less:

var $myDiv = $( "#myDiv" );

if ($myDiv && $myDiv.length) { ... }

However, jQuery selectors always return something that will be interpreted as "truthy", so

if ($('#myDiv')) { 

is a pointless check.