Question

Whenever I want to find if an element exist in the DOM I use the following code.

if($('#target').length){
    // do stuff.
}

This works well and I use it quite a lot on client sites.

Question:
How fast is this method? What are the speed implications when this is used a lot in a project?

Answer 1

You would be much better off using if(document.getElementById('target')) instead. JavaScript is always faster than jQuery (since jQuery is just a bunch of JavaScript hidden under the carpet)

EDIT: If you use it a lot, you can make a custom function:

function idExists(id) {return !!document.getElementById(id);}