removing an event

Question

Hi There!

first, add event listener..

 just like >>>>>> document.addEventListener('MSPointerDown', this.handler_down);

and i will remove event listener..

>>>>>> document.removeEventListener('MSPointerDown', this.handler_down);

it's work well....but

>>>>>> document.addEventListener('MSPointerDown', this.handler_down.bind(this) );     // i just added the binding context at the end of the code...

above event listener is can't remove....

How can I remove such an event listenenr?

Thank you.

Answer 1

Hello,

You need to store the result of your call to `bind` in order to remove it later.  If you read the documentation for `bind` (http://msdn.microsoft.com/en-us/library/ff841995(v=VS.94).aspx), you will see that it returns a new function.  You need will need the reference to that new function.  For example, you could do something like this:

var newHandler = this.handler_down.bind(this);
document.addEventListener('MSPointerDown', newHandler);

// ... Other code ...

document.removeEventListener('MSPointerDown', newHandler);

Answer 2

Cool, thanks Soxley!  

I did't know The bind method return a new function.

Answer 3

Cool, thanks Soxley!  

I did't know The bind method return a new function.

You're welcome!  And indeed it does.

The `bind` implementation basically does this:

Function.prototype.bind = function (context) {
    var self = this;
    return function () {
        self.apply(context, arguments);
    };
};

In other words, this:

var newHandler = this.handler_down.bind(this);

should be equivalent to this:

var self = this,
    newHandler = function () {
        self.handler_down.apply(self, arguments);
    };

// Following code does not change the value of self