Why doesn't functions from Array work on 'arguments'?

Question

Why can't we directly call the functions from Array on arguments?

function f(){
   var x = Array.prototype.slice.call(arguments,1);
   //var x = arguments.slice(1);  **error**
 alert(x);
}

f(1,2,3);

Update: If arguments is not an array object, then how does the Array.prototype.slice function works on an non-array object?

That will simply copy the members of arguments to a new array as if by a simple for loop that iterates over it from 0 to length - 1. Early versions of Opera implemented arguments as an array, but that was not compliant with ECMA-262 so it stopped doing that. — RobG
– RobG, Commented Apr 25, 2014 at 9:46

Quentin · Accepted Answer · 2014-04-25 09:37:53Z

4

Because, despite having some array-like qualities, the arguments object is not an Array.

It is defined independently of, and without reference to, Array objects.

answered Apr 25, 2014 at 9:37

Quentin

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2 Comments

sidgate Over a year ago

So how does the prototype.slice function works on an non-array?

Quentin Over a year ago

The same way as it works on an array. It looks at the value of this and then manipulates it. The arguments object has all the array-like qualities needed by the function. It just doesn't have the function itself.

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