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
    Create a CSS Cube

    CSS cubes really showcase what CSS has become over the years, evolving from simple color and dimension directives to a language capable of creating deep, creative visuals.  Add animation and you've got something really neat.  Unfortunately each CSS cube tutorial I've read is a bit...

  • By
    I’m an Impostor

    This is the hardest thing I've ever had to write, much less admit to myself.  I've written resignation letters from jobs I've loved, I've ended relationships, I've failed at a host of tasks, and let myself down in my life.  All of those feelings were very...

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!