How do I inherit in JavaScript and specify new prototype members as a single object?

Question

I don't like the following since it repeats Child.prototype many times:

function Parent(a)
{
  this.a = a;
}

function Child(a, b)
{
  Parent.call(this, a);
  this.b = b;
}

Child.prototype = Object.create(Parent.prototype);

Child.prototype.constructor = Child;
Child.prototype.childValue = 456;
Child.prototype.anotherChildValue = 457;
Child.prototype.yetAnotherValue = 458;
Child.prototype.IHateToWriteChildPrototypeEachTime = 459;
// ...gazillion more Child.prototype.xxx

I would like the following way of specifying new members instead:

{
  constructor: Child,
  childValue: 456,
  anotherChildValue: 457,
  yetAnotherValue: 458,
  ILoveThisSinceItsSoTerse: 459,
  // ...gazillion more
}

Is there a nice, clean and efficient way of doing this, without creating helper functions and reinventing the wheel in general?

Answer 1

You can make a very simple extend function to do what you wish:

var extend = function(obj, methods) {
  for(var key in methods) {
    if(methods.hasOwnProperty(key)) {
      obj[key] = methods[key];
    }
  }
}

And then you can say:

extend(Child.prototype, {
  constructor: Child,
  foo: function() { }
});