Exploring prototypes & Object.freeze

freeze.js

function makeObj(freeze) {
  var o = {
    foo: "bar",
    doit: function() {
      console.log(this.foo);
    }
  }

  if (freeze)
    Object.freeze(o);
  return o;
}


// A: unfrozen object used as prototype;
try {
  console.log("A");
  var obj = makeObj(false);
  function A() {};
  A.prototype = obj;
  A.prototype.foo = "qux";
  A.prototype.something = function() {
    console.log("wat");
  }

  var a = new A();
  obj.doit();
  a.doit();
  a.something();
}
catch (e) {
  console.error(e)
}


// B: frozen object used as prototype
try {
  console.log("B");
  var obj = makeObj(true);
  function B() {};
  B.prototype = obj;
  B.prototype.foo = "qux";
  B.prototype.something = function() {
    console.log("wat");
  }

  var b = new B();
  obj.doit();
  b.doit();
  b.something();
}
catch (e) {
  console.error(e);
}

// C: frozen object with properties copied to prototype
try {
  console.log("C");
  var obj = makeObj(true);
  function C() {};
  for (key in obj) {
    C.prototype[key] = obj[key];
  }
  C.prototype.foo = "qux";
  C.prototype.something = function() {
    console.log("wat");
  }

  var c = new C();
  obj.doit();
  c.doit();
  c.something();
}
catch (e) {
  console.error(e);
}