Why does JavaScript parser accept JSON as a function body?

Question

The other day, I came across some weird code:

var OrderSupplement = function() {
      oid: null;
      code: "";
      description: "";
      startdate: "";
      enddate: "";
      gender: null;
      cardowner: null;
      box: null;
      divisor: 0;
      created: null;
      createdBy: "";
};

The intention of the code was clear to me: It was the try to define a constructor function, in order to create an instance of OrderSupplement.

I am baffled by this syntax.

The buddy, who wrote the code, said it worked fine - although it obviously does not; at least it does not what it should. He instantiated a new instance of OrderSupplement and set e.g. oid to a nonnull value and retrieved it later. Of course retrieving a value before setting would have unveiled the bug.

The effect of the code above is like:

var OrderSupplementJson = function() {}

My question is:

Why is the code above accepted and does not throw an (syntax) error of any kind?

Answer 1

Because oid: defines a label.

It's syntactically correct but void of anything useful. It's obviously a bug.