Question

Suppose I have this:

var a = { A : { AA : 1 }, B : 2 };

Is there a way for me to create a variable that could allow me to reference either AA or B? What would the syntax look like?

// I know I can do this:    
a['B']; // 2
a['A']['AA']; // 1

// something like this?
var myRef = ???;
a[myRef]; 1 or 2 depending on myRef

If not, what’s a better way to get what I’m going for here?

Answer 1

Not directly.

Solution 1 – use object flattening

Flatten object, to have new object var a = { 'A.AA' : 1; B : 2 };.

See compressing object hierarchies in JavaScript
or Flattening a complex json object for mvc binding to get the javascript function for it.

Soution 2 – write key-path accessor

I can see it was already addressed by Eugen.
Reposted code-reviewed version:

function Leaf(obj,path) {
  path=path.split('.');
  var res=obj;
  for (var i=0;i<path.length;i++) res=res[path[i]];
  return res;
}

Solution 3 – use eval

var x = eval("a." + myRef); // x will be 1 for myRef == "A.AA", 2 for "B"

Be careful with this solution as you may introduce some security issues. It is more of the curiosity.