Select the element

If you’re familiar with jQuery, which I suppose is true, you know how to select an element, for instance if there’s an element with id element_id, you do:

$('#element_id')

If the element exists in the DOM

if ( $('#element_id').length > 0 )
       console.log('the element with element_id
                    exists in the DOM');

Note: that console.log is present as console writing function under FF and Safari only.

if not …

Than $(‘#element_id’).length equals to 0

if ( $('#element_id').length == 0 )
       console.log('the element with element_id
                    don't exists in the DOM');