javascript send arguments object as argument

Question

I need to pass arguments onto a callback function as real arguments. How do I do that? callback requires a variable number of arguments.

Example function like this:

var func = function (callback) {
  doSomething(function () {
    // the goal is to pass on the arguments object to the callback function as real arguments
    callback(arguments)
  });
}

Thanks in advance.

It might be a similar question to this: Is it possible to send a variable number of arguments to a JavaScript function?

But I didn't understand that question nor the answers.

Edit: If possible, I would like to not pollute global.

Anurag · Accepted Answer · 2011-03-28 09:48:10Z

18

Use apply to invoke the callback so the array items gets passed as individual arguments to the function.

callback.apply(this, arguments);

apply takes the context, and an array as an argument, and each item of the array can be passed as a named argument of the function being invoked.

function two(first, second) {
    alert(first), alert(second);
}

two.apply(null, ["Hello", "World"]); // alerts "Hello", then "World"

Implementations of ES3 required that the second argument to apply be either an array, or an arguments object. ES5 makes it more liberal in that as long as it resembles an array - has a length property, and corresponding integer indexes, it will work.

edited Mar 28, 2011 at 9:48

answered Mar 28, 2011 at 9:14

Anurag

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7 Comments

Harry Over a year ago

Why apply null instead of this?

HBP Over a year ago

allpy takes two arguments, the obejct which becomes this in the called function and an array whic becmes the arguments. So your line should read callback.apply(this, Array.prototype.slice.apply(arguments));

user447356 Over a year ago

Yep, I've messed up with this before seeing your answer came up with something similar: jsfiddle.net/yahavbr/HYTJL

Anurag Over a year ago

I'm not using this in any special manner inside the function two, so it doesn't really matter what we pass as context to apply. We could've passed in anything - two.apply("dontCare", ["Hello", "World"]).

Anurag Over a year ago

@Hans - thanks for the correction, I'm missing the context as the first argument.

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