events - How can i check if a JavaScript-Eventhandler has been set?

Question

I've got a JavaScript-function that sets the "onclick"-event of some HTML-Nodes - even if that "onclick"-event has been set before.

How can i check if that event has already been set, so I can extend my function to set the event only on HTML-Nodes where it has not already been set?

Answer 1

Check, like this:

if(typeof someNode.onclick == "function") {
   // someNode has an event handler already set for the onclick event...
}

By the way, if you are using a library, you should say so - if you are, it might be easier/cleaner and would differ based on which library you are using...