Javascript removeEventListener not working

Question

I have the following code to add eventListener

 area.addEventListener('click',function(event) {               app.addSpot(event.clientX,event.clientY);               app.addFlag = 1;           },true); 

It is working correctly as expected..Later in another function i tried to remove the event listener using the following code

 area.removeEventListener('click',function(event) {               app.addSpot(event.clientX,event.clientY);               app.addFlag = 1;           },true); 

But the even listener is not removed..Why is it happening?Is there any problem with my removeEventListener()? Note:Here area is something like document.getElementById('myId')

Answer 1

This is because that two anonymous functions are completely different functions. Your removeEventListener's argument is not a reference to the function object that was previously attached.

function foo(event) {               app.addSpot(event.clientX,event.clientY);               app.addFlag = 1;           }  area.addEventListener('click',foo,true);  area.removeEventListener('click',foo,true); 

Answer 2

I find that for the windows object, the last param "true" is required. The remove doesn't work if there is no capture flag.