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Convert arguments to Array

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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.

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Discussion

  1. Brandon Benvie

    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. dreadcast

    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. Raja

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

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