object.create和new Object之间的原型区别

Question

//The last link of the prototype chain always be Object.prototype. 
var o = {"name":"kannanrbk", "age": 21};
//extending object.
var no = Object.create(o); //Now the new object is linked to the old object o. 
no.name = "Bharathi Kannan R";
console.log(o.name); //Still be 'kannanrbk'. Because, this prototype chain will be used only for retrieval.
//In js prototype is dynamic. If we add new property in this prototype. It will be visible immediately. 
o.sex = "Male";
console.log(no.sex);

//To find the property of the type 
console.log(typeof no.sex);

/**
* Enumeration
*/
for(var k in no) {
    console.log(no[k]);
}

//To check whether the property is belongs to the object.
console.log(no.hasOwnProperty('sex')); //false, it won't check the prototype chain.

var p = {"name":"kannanrbk","age":23};
var np = new Object(p);

//Why it returns true?
console.log(np.hasOwnProperty('age')); //true. 
np.age = 25;

//How the value is updated in entire prototype chain?
console.log(p.age);

What is the difference between Object.create and new Object(old)?

Answer 1

Quoting MDN's documentation on Object ,

The Object constructor creates an object wrapper for the given value. If the value is null or undefined , it will create and return an empty object, otherwise, it will return an object of a Type that corresponds to the given value. If the value is an object already, it will return the value.

The bold text is the key here. If you pass an object to Object , it will return the object as it is. That is why,

console.log(np.hasOwnProperty('age'));

return true . You can do one more check, like this

var p = {
    "name": "kannanrbk",
    "age": 23
};
var np = new Object(p);

console.log(np === p);
# true

because np and p are one and the same. Here, no prototype chain is established.

But, when you use Object.create , the parameter you pass to that will be used as the prototype of the object created, so the prototype chain will be established in that case. Quoting Object.create 's MDN documentation ,

The Object.create() method creates a new object with the specified prototype object and properties.