variable define but not working in javascript while this represent window

Question

i have a little code snippet below

var foo = {
    bar: function () {
        return this.baz;
    },
    baz: 1
};
(function () {
    return typeof arguments[0]();
})(foo.bar);
baz = 1;
//result undefined

when the foo.bar function is executed, this refers to the window scope which of course knows nothing about baz so i have defined baz=1 in window. but the program still not working and returning undefined. why it is returning undefined while baz have defined in window and i am executing foo.bar from window

adding a blank line before your code would make it display correctly. — rhgb
– rhgb, Commented Mar 7, 2014 at 6:35
If you do bar: function () { console.log(this); return this.baz; } you can see that this refers to its parent, which is arguments. — Derek 朕會功夫
– Derek 朕會功夫, Commented Mar 7, 2014 at 6:45

xdazz · Accepted Answer · 2014-03-07 06:42:24Z

7

When you execute the function like arguments[0](), then this is referring to the arguments object, which doesn't have the property baz, so it will still be undefined.

You could bind this to a certain object by:

arguments[0].call(foo) or arguments[0].apply(foo).

answered Mar 7, 2014 at 6:42

xdazz

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shredmill · Accepted Answer · 2014-03-07 06:43:04Z

0

"this" becomes scoped the bar function. If you change it to return foo.baz, it'll work

answered Mar 7, 2014 at 6:43

shredmill

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halkujabra · Accepted Answer · 2014-03-07 06:46:53Z

-1

foo.baz will work , but not this.baz. try reading the scopes in javascript

answered Mar 7, 2014 at 6:46

halkujabra

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1 Comment

Ry- Over a year ago

Because “try reading the scopes in javascript” doesn’t make sense, and this doesn’t answer the actual question of “why”.

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