Advanced JavaScript: Compose function

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18 points·heseltine··6 comments

@apphacker - are you sure? I thought bind assigned the value of 'this' in a function.

We have nested comments here. You don't have to use @; you can reply directly.

What is 'call' doing in that function? Check out dojo.hitch:

http://www.google.com/codesearch/p?hl=en#1oUPVh-C1Wg/trunk/e...

This is simply bind which will be in future versions of JavaScript. http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more... It has been available in dojo as dojo.hitch, goog.bind, $.hitch in a jQuery plugin.

No, it's function composition as seen in e.g. pure functional programming languages like Haskell:

(.) :: (b -> c) -> (a -> b) -> a -> c

Except that of course in an impure language like JavaScript if you compose some function f with another function g, either or both functions could have side effects (via I/O, mutation etc.) that break referential transparency.

After a quick glance at the Prototype code, the bind function isn't merely changing which object the name 'this' is bound to, it also allows a kind of currying. However, this still isn't function composition.

Look at the source of what dojo.hitch does or google.bind. It is the exact same thing. Whoever down-voted me obviously doesn't know JavaScript. Voting on comments is such a dumb idea. Popularity does not equal right. Right is simply right.

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