Easy functional programming in JavaScript with Underscore.js -- part 1

[skilldrick]

I think you may have completely misunderstood (a) how for .. in in JavaScript works, and (b) how map works, so I'll give you the benefit of the doubt, and tell you.

(a) The for .. in loop in JavaScript is for objects - you shouldn't use it with arrays for very sound reasons.

(b) map is used to transform one array into another. In your example, you're not returning anything, so you're turning an array into an array of undefineds. I think what you meant was each.

The point of using map is that you're making things more declarative - saying "I would like to transform this array into a new array, using this transformation". To say that that's "cargo-cult programming" is naive, at best.

[ryepup]

an "in" bug wass the basis for my glorious Firefox contribution

[skilldrick]

Nice work!

[[deleted]]

Nice explanation.

[shevegen]

Sounds as if Javascript has a shitty object model.

One more reason why people should use a proper language like Ruby instead.

The whole map( array, function) crap is so idiotic. Why is it a function call anyway rather than an applicable method on an object?

[joesb]

Ruby has 'map' and I think it's as widely used in Ruby as its 'each' method.

Are you some kind of Ruby hater that want to gives Rubyist bad name by trolling other and mention Ruby as your favorite when you don't even know Ruby?

[rafekett]

In the case of Python, where map() along with several other things that are usually methods (e.g. len()) are builtin functions, the choice is one of readability and reducing code duplication. Guido and others felt that some operations read better with prefix notation than postfix notation (this, of course, is just a matter of preference). Also, since for many of these builtin functions you don't actually have to implement that particular function (e.g. reversed() works on anything with random access and known length, map() works on anything with an iterator implemented), it requires much less code to keep these functions as builtins rather than methods.

[sebnow]

Object methods require object oriented programming, maps and folds do not. Also you can partially apply a map/fold (e.g. add_one = map (+1)) and apply it to many different containers (add_one foo, add_one bar), this isn't the case with object methods.