Question

When I add an .on() event listener twice with the same function, it fires the function twice.
Example: 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');