What does arguments reference when used as an argument?

Question

Here is _.extend from underscore.

  // Extend a given object with all the properties in passed-in object(s).
  _.extend = function(obj) {
    each(slice.call(arguments, 1), function(source) {
      if (source) {
        for (var prop in source) {
          obj[prop] = source[prop];
        }
      }
    });
    return obj;
  };

The function call expects a this value followed by a list of arguments.

If the only argument passed is '1', then slice will return an array omitting the first item.

However, how can arguments be used as a this value as defined my MDN.

MDN

call

slice

arguments

duplicate of [why does array slice convert javascript arguments to array](http://stackoverflow.com/questions/14327339/why-does-array-slice-convert-javascript-arguments-to-array) — Bergi, Feb 25 '13 at 22:06
`arguments` is an array-like object, containing a reference to each argument passed to the function. — Felix Kling, Feb 25 '13 at 22:07

score 1 · Answer 1 · answered Feb 25 '13 at 21:59

1

The same thing it always references, the arguments passed to the containing function.

answered Feb 25 '13 at 21:59

score 1 · Accepted Answer · answered Feb 25 '13 at 22:03

1

Using arguments as the this value applies the function to arguments. It would be like doing arguments.slice(1), except you can't because arguments is technically not an array.

answered Feb 25 '13 at 22:03

Andrew Kirkegaard

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score 0 · Answer 3 · answered Feb 25 '13 at 22:00

0

I believe "this" is implied. Sometimes you have to "force" a fake list to apply to some Array prototypes else it won't work.

I might be misunderstanding your questions, if so - I apologize.

answered Feb 25 '13 at 22:00

james emanon

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What does arguments reference when used as an argument?

3 Answers3