javascript - Add an event listener with sevral parameters and remove it later

Question

This seems to be a very popular question though i didn't seem to find any pertinat answers.

I attach an event listen like :

window.addEventListener('scroll', fnName, false);

The problem is that fnName expect several parameters, so i then triedl

window.addEventListener('scroll', (function( e ){
   return fnName(e, some, param )
}()), false)

but then window.removeEventListener do not work anymore so i tried:

window.removeEventListener('scroll', (function( e ){
   return fnName(e, some, param )
}()), false)

Answer 1

Every time you declare an anonymous function, it creates a new function instance. If you want to remove an existing function, you need to retain a copy of the function instance.

var temp = function () {
    fnName(e, some, param);
};
window.addEventListener('scroll', temp, false);
//elsewhere,
window.removeEventListener('scroll', temp, false);

---

I should also note that using

(function (e){
     return fnName(e, some, param)
}());

calls fnName immediately with undefined as the first parameter. I doubt that's your intention.