Convert arguments to Array

By  on  

The arguments object thats automatically available within functions can be a source of confusion for some people; it's kind of an array but it's kinda not. JavaScript is awesome in that you can pass any number of arguments to a function, and oftentimes developers need to iterate over every argument provided.  The arguments object doesn't have a forEach method, but using a quick JavaScript technique, you can convert arguments to an array:

function myFn(/* any number of arguments */) {
	var args = Array.prototype.slice.call(arguments);
		// or [].slice.call(arguments)

	args.forEach(function(arg) {
		// do something with args here
	});
}

Much like converting a NodeList to an array, Array's slice method takes the arguments object and converts it to a true array, allowing for forEach, map, and traditional array iteration.  Keep that trick up your sleeve for future development.

Recent Features

  • By
    CSS vs. JS Animation: Which is Faster?

    How is it possible that JavaScript-based animation has secretly always been as fast — or faster — than CSS transitions? And, how is it possible that Adobe and Google consistently release media-rich mobile sites that rival the performance of native apps? This article serves as a point-by-point...

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

Incredible Demos

Discussion

  1. If you’re using Firefox, or in the future when other browsers support ES6, you can do it more elegantly:

    function myFn(...args) {
      /* code */
    }
  2. In case you are using Mootools, Array.from does the job, isn’t it ?

  3. Dmitry Tsvettsikh

    Why not it:

    var args = Array.apply(null, arguments);
    
    • David

      You can do that but be aware if you do something like:

        function x(){
         return Array.apply(null, arguments);
        };
        x(10); //=> it will return empty array with a length of 10 instead of [10]
      
  4. islomjon

    Cool trick, but why even typeof arguments returns object?

  5. We have a new method, Array.from(arguments)

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!