Justin Li


Javascript Arguments

2007-09-15

Why the arguments variable is not an Array in Javascript always baffles me. The fact that it's an "Array-like Object" with the length attribute makes it worse.

Coming from Lisp, I would like to pass all subsequent (optional) arguments after a point to another function. For example:

function foo(a, b) { ... bar(arguments.slice(2)); ...}

But of course arguments doesn't have the slice function. In Lisp, it would be something like (forgive me if my Lisp is rusty):

(defun foo (a b &rest others) ... (bar others) ...)

In the code for my calendar, I duplicate the code I need, since it's only a short three lines. Otherwise, I would have to use Array.prototype.slice.call(...) to turn it into an array before slice-ing, like so:

function foo(a, b) { ... bar.apply(this, Array.prototype.slice.call(arguments).slice(2)); ...}

Stupid. The other thing is that Javascript calls itself a functional language, when some functions return useless values. But that's another issue.

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