How to call a function when we have its arguments in an array

Question

Let's say we have a function

f = function(a, b, c){
    // do something important
}

and an array containing the arguments

var args = [5, 'string', 12] // just any values

Obviously, I could call my function like this :

f(args[0], args[1], args[2])

This is really not elegant, and I look for a better way to accomplish this. Thanks for your suggestions.

You'll want to see call and apply; in particular, apply applies here. — Waleed Khan
– Waleed Khan, Commented Oct 29, 2013 at 18:09

Mike Edwards · Accepted Answer · 2013-10-29 18:09:09Z

3

You are looking for Function.apply()

f.apply(window, args); // pass something other than null to set 'this' within the call

answered Oct 29, 2013 at 18:09

Mike Edwards

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2 Comments

dandavis Over a year ago

note that you can't use apply() if you use "new ", you'll have to manually fill-in the parameters until ES6 is widely supported.

Blue Skies Over a year ago

@dandavis: Or var o = Object.create(f.prototype); f.apply(o, args);

Vivin Paliath · Accepted Answer · 2013-10-29 18:10:42Z

1

Use .apply(). The second argument lets you specify an array of arguments to the function you are trying to call. The first argument is the value of this you want in the context of the function.

So in your case it would be:

f.apply(null, args);

or

f.apply(window, args);

If you want this within the context of f to be the window object.

answered Oct 29, 2013 at 18:10

Vivin Paliath

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Comments

Blue Skies · Accepted Answer · 2013-10-29 18:09:15Z

1

Use .apply().

f.apply(window, args);

This will work with any array-like object in the second argument position.

It invokes the function f, and sets the first argument you pass as its this value (here I just used window), and distributes the members of the second argument as individual arguments to the function.

The result is as though you had done this:

f(5, 'string', 12);

There's a counterpart to the Function.prototype.apply method called .call(). The .call() method is exactly the same, except that you pass the arguments individually.

f.call(window, 5, 'string, 12);

The purpose of this is the call the function like normal, but set the this value manually.

answered Oct 29, 2013 at 18:09

Blue Skies

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Comments

gasp · Accepted Answer · 2013-10-29 18:14:33Z

-1

It depends of your needs (of course)

if elements are homogenous

var sum = function(numbers) {
   // do some calculations
}

var randomees = [5, 6, 12]
var total = sum(randomees);

If they are not, they should have some kind of description. I.e. if you are defining options or parameters, then you would consider this

var parameters = {
    size:13,
    shipped:true,
    description:"Laptop"
}

var displayLaptop = function(characteristics) {
    console.log(characteristics.size)
}

(or even play with some jQuery.extend ish method)

answered Oct 29, 2013 at 18:14

gasp

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