CODEWITHSUNDEEP
javascript
Jatin
Jatin

Reputation: 4063

Scope of Variables declared within javascript object

I was trying to understand the scope of variables in javascript objects. But the behavior that I am getting seems to be a little off the road. To put it simply, if I have an object that defines a function as a variable, then the function variable is not able to access other variables of the object in which it is defines. The code below will make things clear.

<html>
<head>
    <script type="text/javascript">

        var someObject = {
            someVariable : 5,
            getVariable: function() {
                return someVariable;
            }
        };

        window.onload = function () {
            alert(someObject.getVariable());
        };

    </script>
</head>
<body>
    Hello There
</body>
</html>

The above code gives "ReferenceError: someVariable is not defined" for the someVariable in function getVariable(). Would anyone like to comment on this behavior?

Upvotes: 1

Views: 126

Answers (3)

LetterEh
LetterEh

Reputation: 26696

Absolutely.

The "variable" you're talking about isn't a "variable", it's a property of an object (the object happening to be a variable).

As such, you have two options.
Assuming that your object is made like this:

var obj = {
    property : 42,
    everything : function () { /* ... */ }
};

The two options for inside of your function body, to return the value 42 are:

obj.property;

OR

this.property;

When you call:

obj.everything();

The JS interpreter will see obj as being equal to this inside of the function.
Or you reference obj itself, directly, and access property using either .property dot-notation, or ["property"] bracket-notation.

Upvotes: 3

Thilo
Thilo

Reputation: 262474

That is not a variable, that is a property/field of an object.

Try this.someVariable.

Here this is a (rather special) variable that points to the object, and the dot (or square bracket) syntax can be used to access fields of that object.

You can also do someObject.someVariable in places where someObject (another variable pointing at the object) is in scope.

Upvotes: 1

Korikulum
Korikulum

Reputation: 2599

Try this.someVariable:

var someObject = {
        someVariable: 5,
        getVariable: function () {
            return this.someVariable;
        }
    };

window.onload = function () {
    alert(someObject.getVariable());
};

Upvotes: 0

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