jQuery determining if element exists on page

Question

How can I determine if an element exists on a page... for instance...

$(\'select[name=\"modifier_option\"]\')

If that select box exists on

Answer 1

copy/paste from here: Is there an "exists" function for jQuery?

jQuery.fn.exists = function(){return jQuery(this).length>0;}

if ($(selector).exists()) {
    // Do something
}