Object.freeze()

var obj = {
  prop: function () {},
  foo: "bar",
};

//    ,      
obj.foo = "baz";
obj.lumpy = "woof";
delete obj.prop;

//   ,      .
//       .
var o = Object.freeze(obj);

o === obj; // true
Object.isFrozen(obj); // === true;

//       
obj.foo = "quux"; //    
obj.quaxxor = "the friendly duck"; //    

// ...         TypeError
function fail() {
  "use strict";
  obj.foo = "sparky"; //  TypeError
  delete obj.quaxxor; //  TypeError
  obj.sparky = "arf"; //  TypeError
}

fail();

//      Object.defineProperty   
Object.defineProperty(obj, "ohai", { value: 17 }); //  TypeError
Object.defineProperty(obj, "foo", { value: "eit" }); //  TypeError

obj = {
  internal: {},
};

Object.freeze(obj);
obj.internal.a = "A";

obj.internal.a; // 'A'

//    obj  ,      obj.
//     .
function deepFreeze(obj) {
  //      obj
  var propNames = Object.getOwnPropertyNames(obj);

  //      
  propNames.forEach(function (name) {
    var prop = obj[name];

    //   prop,   
    if (typeof prop == "object" && prop !== null) deepFreeze(prop);
  });

  //    obj (  ,    )
  return Object.freeze(obj);
}

obj2 = {
  internal: {},
};

deepFreeze(obj2);
obj2.internal.a = "";
obj2.internal.a; // undefined

> Object.freeze(1)
TypeError: 1 is not an object //  ES5

> Object.freeze(1)
1                             //  ES2015