Comments on: placeholders and currying

By: klaush

klaush — Wed, 10 Mar 2010 15:00:55 +0000

the curry functions only works for simple args, imagin
func( {animate:false,load:true,icon:false},html){
dosomething
}

currying this function destroy the object, so you will need to add an object/array parser aswell

By: Javascript geek

Javascript geek — Thu, 05 Nov 2009 18:58:38 +0000

not only that but:
js> var _,x
js> _ === x
true

var _ = {} is much better, also why is this not in fn.js on github?

By: Karl

Karl — Thu, 05 Nov 2009 18:04:35 +0000

See Oliver Steele’s partial() in his functional library for the exact same functionality. :)

I’ve also seen this done with undefined as the test with the advantage of namespace cleanliness and the disadvantage of having to type undefined.

By: youngnh

youngnh — Thu, 05 Nov 2009 17:52:43 +0000

so this isn’t a value thing.

functions could expect an empty object to be passed to them and if I just looked for an empty object, I might mistake a real value for a placeholder.

I want to know if the function has been given the _ variable itself. I’m interested in it’s reference.

if you’ll notice, I made a === check instead of a == equals check, as the former is stricter, only returning true when you compare an object to itself, and the latter returning true when two objects have the same value.

By: benjaminplee

benjaminplee — Thu, 05 Nov 2009 17:36:08 +0000

I too was wondering about that.

I am still trying to wrap my head around curring and a few other Functional Programming concepts. Functions as first class citizens which can be passed and invoked in different contexts is easy to understand and follow. Transforming functions and returning new ones is a bit harder to follow given my OO background. Good post though.

Also, presumably, a language that supported named method parameters would allow you to not worry about order and know what params have not yet been defined.

By: Tom Robinson

Tom Robinson — Thu, 05 Nov 2009 17:21:22 +0000

You should probably assign an object to the underscore, otherwise any argument which is undefined will match:

js> var _
js> _ == undefined
true

Just doing “var _ = {}” should be sufficient.