javascript原型继承如何用于Array函数

Question

I need to understand how the Array object gets a reference to Object .

For example, when I create var arr = []; it has Array.prototype ---> Object.prototype ---> null .

I want to achieve above for the example below:

Suppose I have a function xyz() , where xyz.prototype.somefunction = function() { } .

I have another function abc() , where abc.prototype.anotherfunction = function() { } .

When I create an object of abc() — as in var obj = new abc() — I want it to have a prototype chain like obj ---> abc.prototype ---> xyz.prototype ---> object.prototype ---> null .

Please suggest the best way to do this.

Answer 1

function xyz() {}
function abc() {}
var p = new xyz();
abc.prototype = p;

var o = new abc();
o.__proto__ === p // true
o.__proto__.__proto__ === xyz.prototype // true
o.__proto__.__proto__.__proto__ === Object.prototype // true
o.__proto__.__proto__.__proto__.__proto__ === null // true

Or:

function xyz() {}
function abc() {}
var p = Object.create(xyz.prototype);
abc.prototype = p;    

var o = new abc();
o.__proto__ === p // true
o.__proto__.__proto__ === xyz.prototype // true
o.__proto__.__proto__.__proto__ === Object.prototype // true
o.__proto__.__proto__.__proto__.__proto__ === null // true

Or:

class xyz {}
class abc extends xyz {}

var o = new abc();
o.__proto__.__proto__ === xyz.prototype // true
o.__proto__.__proto__.__proto__ === Object.prototype // true
o.__proto__.__proto__.__proto__.__proto__ === null // true

Or:

function xyz () {}
const abc = {
    __proto__: Object.create(xyz.prototype)
}

abc.__proto__.__proto__ === xyz.prototype // true
abc.__proto__.__proto__.__proto__ === Object.prototype // true
abc.__proto__.__proto__.__proto__.__proto__ === null // true

Or:

function xyz () {}
function abc() {}
Object.setPrototypeOf(abc.prototype, xyz.prototype);

var o = new abc();
o.__proto__.__proto__ === xyz.prototype // true
o.__proto__.__proto__.__proto__ === Object.prototype // true
o.__proto__.__proto__.__proto__.__proto__ === null // true

Answer 2

You can do prototypical inheritance:

abc.prototype = new xyz();

now, when you create a new object, it will follow the chain you desire.