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 the screen I need to validate it's value on the page to ensure it's value is > 0, but if it doesn't exist I don't need to worry about it.

Answer 1

    if( $('select[name="modifier_option"]').length )
{
     // it exists
}

Answer 2

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
}