javascript - What is the difference between using Object.create() and using assignment operator?

Question

Here are a few examples.

// case 1:
var obj1 = {msg : 'Hello'};
var obj2 = obj1;
obj2.msg = "Hi!"; //overwrites
alert(obj1.msg); //=>'Hi!'

// case 2:
var obj1 = {msg : 'Hello'};
var obj2 = Object.create(obj1);
obj2.msg = "Hi!"; //does not overwrite
alert(obj1.msg); //=>'Hello'

// case 3:
var obj1 = {data: { msg : 'Hello'}}
var obj2 = Object.create(obj1);
obj2.data.msg = "Hi!"; //overwrites, Why?
alert(obj1.data.msg); //=>'Hi!'

I think Object.create() just gives both makes both point to the same prototype, while assignment makes both object point to same location(not just prototype). But then why is the data object being overwritten in case 3?

Answer 1

Because Object.create() only creates a shallow copy, nested objects are still referenced and not copied deeply, see 15.2.3.5 (Object.create()) and 15.2.2.1 (new Object()).

If you want to clone an object entirely have a look at How do I correctly clone a JavaScript object? and similar questions.