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Accessing previous values ​​inside an object during declaration

Possible duplicate:
Self-promotions in object literal declarations

var obj = {
    value: 10,
    value2: value + 2
};

How can i do this? (Assuming it's possible)

I use a lot of jQuery $.extend

to add more properties that rely on previous added values; so changing a few values ​​automatically adjusts the rest.

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2 answers


You cannot do this in a declaration, but you can always make a function. The following values ​​will always return a value of 2 greater than the value stored in the value:

var obj = {
    value: 10,
    getValue2: function(){ return this.value + 2; }
};


If you don't want value2 to change along with the value, you can declare a placeholder variable and declare an object using this:

var placeholder = 10;

var obj = {
    value: placeholder,
    value2: placeholder + 2
};
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I'm not 100% sure if you can do this during the announcement. You could, however, do this afterwards:

using an extension:

var obj = {
    value: 10
};

$.extend(obj, {
    value2: obj.value + 2
});

http://jsfiddle.net/KgKgf/



just javascript:

var obj = {
    value: 10
};

obj.value2 = obj.value + 2;

http://jsfiddle.net/KgKgf/1/

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