Why doesn't .join() work with function arguments?

Question

Why does this work (returns \"one, two, three\"):

var words = [\'one\', \'two\', \'three\'];
$(\"#main\").append(\'
\' + words.join(\", \") + \'

        

Answer 1

You can use typeof to see what's happening here:

>>> typeof(['one', 'two', 'three'])
"object"
>>> typeof(['one', 'two', 'three'].join)
"function"
>>> typeof(arguments)
"object"
>>> typeof(arguments.join)
"undefined"

Here you can see that typeof returns "object" in both cases but only one of the objects has a join function defined.

Answer 2

Just use the jQuery utility function makeArray

arguments is not an Array, it is an object. But, since it so "array-like", you can call the jQuery utility function makeArray to make it work:

var displayIt = function() {
    return 'the list: ' + $.makeArray(arguments).join(",");
}   
$("#main").append('<p>' + displayIt('111', '222', '333') + '</p>');

Which will output:

<p>the list: 111,222,333</p>