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
};
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.
No and yes.
The following aren't possible:
var o = {
a : 42,
b : o.a //raises a TypeError, o is not defined
};
var o = {
a : b : 42 //raises a SyntaxError, unexpected :
};
The following, however, are:
//referencing a pre-existing variable is obviously possible
var ans = 42;
var o = {
a : ans,
b : ans
};
var o = {
a : 42
};
//after the variable has been declared, you can access it as usual
o.b = o.a;
If you feel limited by the value being a single statement, you can always use an anonymous function:
var o = {
a : (function () {
doStuff();
return otherStuff();
}())
};
to keep your example:
var test = {
prop1: obj1,
prop2: obj2,
prop3: (function () {
return (test.prop1!=null)?test.prop1:test.prop2;
})()
};
