How to check if an elem is already listening for a function

Question

When I add an .on() event listener twice with the same function, it fires the function twice.. ex: http://jsfiddle.net/56hxy/13/ (click the 'on' button, then click on the main green div)

How to check if an elem is already listening for a function so as to not add it twice?

if (already  $('#id').on('click',functionName)  ) 

Answer 1

You can unbind the event listner and then add it.

To unbind it use

$('#id').unbind('click');

Answer 2

Duplicate of this question? You can use the $._data method, although it's internal so probably not ideal.

Anyway it would be like: $._data($("#id")[0], "events")