Kangax...
2) Non-bound event handler is faster at run time, as it accesses
> `onClick` from the proper object directly, but presumably consumes
> more memory (due to extra closure, created during function expression
> evaluation)
>
There is no "extra" closure because .bind() creates a closure anyway
(because just calling .apply would execute the function right away);
bind: function() {
> if (arguments.length < 2 && Object.isUndefined(arguments[0])) return
> this;
> var __method = this, args = $A(arguments), object = args.shift();
> return function() {
> return __method.apply(object, args.concat($A(arguments)));
> }
> }
So in all cases, it's less overhead to just not use .bind(). It's purely a
convenience method.
Ryan Gahl
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On Tue, Mar 10, 2009 at 4:53 PM, kangax <[email protected]> wrote:
>
> On Mar 10, 3:27 pm, "T.J. Crowder" <[email protected]> wrote:
> > > I do agree there are just times when .bind() is called for, but I am
> fairly
> > > certain the majority of people WAY overuse it.
> >
> > +1 to that, where you're defining the function inline. Where you're
> > not, while this may be faster:
> >
> > var self = this;
> > handler = function() {
> > self.realHandler();
> > }
> >
> > ...bind is (for me) much clearer:
> >
> > handler = realHandler.bind(this);
> >
> > But again, yeah, when you're defining the function inline _anyway_,
> > take advantage of the native closure stuff.
>
> I absolutely agree that not using `bind` with local function works
> well and works fast. I also agree that `bind` is overused. What I want
> to stress, though, is that when binding a non-local function, `bind`
> actually *eliminates an extra closure* that would otherwise be
> implicitly created. You either save on memory, or on runtime
> performance:
>
> 1) Bound event handler is augmented and is slower than original one
> (at runtime), as it has to go through function call, `apply`
> invocation and even worse - `$A` normalization, etc. (in older
> versions of prototype)
>
> this.element.observe('click', this.onClick.bind(this));
>
>
> 2) Non-bound event handler is faster at run time, as it accesses
> `onClick` from the proper object directly, but presumably consumes
> more memory (due to extra closure, created during function expression
> evaluation)
>
> var self = this;
> this.element.observe('click', function(){ self.onClick() });
>
> [...]
>
> --
> kangax
> >
>
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