Question

I have clearly got this wrong (because it doesn’t work) but I thought the following two code blocks where functional identical, but one is working as expected, the other is not.

Working:

mfObject.questions = {}
mfObject.questions.active = "#"+$('.ui-page-active').attr('id');

Not Working:

mfObject.questions = {
    active : "#"+$('.ui-page-active').attr('id');
}

Answer 1

You should not have a ; at the end of the property assignment.

mfObject.questions = {
    active : "#"+$('.ui-page-active').attr('id') // <-- no semicolon here
}

Properties assigned inside an object literal are separated by commas if there are multiple assignments, and semicolons would never appear as terminators to a property assignment (though they may be present internally if you assigned a function to a property).

// Correct property assignment in an object literal
mfObject.questions = {
  active: "someval",
  prop1: "someval1",
  prop2: "someval2",
  prop3: function() {
    console.log("I have semicolon terminators in a function");
    console.log("because I have multiple statements");
  },
  prop4: "someval4"
};