Javascript Scope in Injected Function

Question

(function(){
    var privateSomething = "Boom!";
    var fn = function(){}
    fn.addFunc = function(obj) {
        alert('Yeah i can do this: '+privateSomething);
        for(var i in obj) fn[i] = obj[i];
    }
    window.fn=fn;
})();

fn.addFunc({
    whereAmI:function()
    {
        alert('Nope I\'ll get an error here: '+privateSomething);
    }
});

fn.whereAmI();

Why can't whereAmI() access privateSomething? and how do i place whereAmI() in the same context as addFunc()?

Ned Batchelder · Accepted Answer · 2012-07-21 11:47:00Z

4

Javascript is lexically scoped: a name refers to variables based on where the name is defined, not where the name is used. privateSomething is looked for as a local in whereAmI, and then in the global scope. It isn't found in either of those places.

answered Jul 21, 2012 at 11:47

Ned Batchelder

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Comments

1983 · Accepted Answer · 2012-07-21 14:05:31Z

2

JavaScript has lexical scoping, not dynamic scoping (apart from this). See http://en.wikipedia.org/wiki/Scope_(computer_science)#Lexical_scoping_and_dynamic_scoping

edited Jul 21, 2012 at 14:05

answered Jul 21, 2012 at 11:48

1983

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4 Comments

Esailija Over a year ago

this is a keyword not a variable. It has nothing to do with scope.

lilturtle Over a year ago

Gotcha. So no go on getting at that variable huh?

1983 Over a year ago

this is a reference to an object (or undefined), and it is resolved dynamically.

lilturtle Over a year ago

i think this is a keyword and everything to do with scope.

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