Declaring global variables without a value

Question

I wish to create a JavaScript object with nested global variables where some of the variables will not have a default value specified.

I currently have this:

var globalVarA = "foo";
var globalVarB = "bar";
var globalVarC;

function myFunction(){
  //do something
}

I wish to change this to:

var myObject = {
  GlobalVars: {
     globalVarA: "foo",
     globalVarB: "bar",
     globalVarC
  },
  myFunction: function(){
     //do something
  }
}

However I get the following error:

Expected ':'

How can I declare this variable without a value?

Answer 1

If you want to define the variables as properties of GlobalVars you have to explicitly assign undefined to them

GlobalVars: {
     globalVarA: "foo",
     globalVarB: "bar",
     globalVarC: undefined
  },

Your code contained invalid notation, when using object literal notation you must specify a value for each variable. This is unlike other notations like XML or formParams where you can declare a attribute/property without setting it.

Note, that in my solution undefined variables do get a default value - that value is just the primitive value undefined which is what is returned by default for variables that were not defined.

However, your variable does get defined if you do globalVarC: undefined

GlobalVars.globalVarC;//undefined
GlobalVars.globalVarX;//undefined
GlobalVars.hasOwnProperty("globalVarC");//true
GlobalVars.hasOwnProperty("globalVarX");//false

From the spec:

4.3.9 undefined value:

primitive value used when a variable has not been assigned a value.