Question

I’m creating an object using literal notation. Is it possible to have some of the properties use previously defined properties as their value?

For example:

    var test = {
        prop1: obj1, 
        prop2: obj2,
        prop3: (prop1!=null)?prop1:prop2
    };

Answer 1

If you are trying to do something like var x = { 'a': 1, 'b': x.a } then it won’t work. Since x is not finished being defined.

But you can do something like

var
    a = 12,
    b = 24,
    c = a + b; // 36

This is because each var definition is interpreted sequentially. Basically equivalent to

var a = 12;
var b = 24;
var c = a + b;

But with objects and arrays the entire definition is interpreted one time.