JavaScript Object.setPrototypeOf() Method

The Object.setPrototypeOf() method sets the prototype (i.e., the internal [[Prototype]] property) of a specified object to another object or null. All JavaScript objects inherit properties and methods from a prototype. It is generally considered the proper way to set the prototype of an object.

Syntax:

Parameters:

obj: It is the object which is to have its prototype set.

Prototype: It is the object's new prototype (an object or null).

Return value:

This method returns the specified object.

Browser Support:

Chrome	34
Edge	Yes
Firefox	31
Opera	Yes

Example 1

let raay = {
  drive() {
    return 'Add raay';
  }
}
let naty  = {
  net() {
    return 'use net';
  }
}
// Set raay's __proto__ to naty's  __proto__'s  __proto__
Object.setPrototypeOf(naty, raay);

console.dir(naty); //prints the naty object
console.log(naty.net()); // use net
console.log(naty.drive()); // Add raay

Output:

 [object Object] {
  drive: drive() {
    return 'Add raay';
  },
  net: net() {
    return 'use net';
  }
}
"use net"
"Add raay"

Example 2

 var Animal = {
   speak() {
     console.log(this.name + ' makes');
   }
};

class Dog {
   constructor(name) {
   this.name = name;
  }
}

Object.setPrototypeOf(Dog.prototype, Animal); 
// If you do not do this you will get a TypeError when you invoke speak
var d = new Dog('people');
d.speak();

Output:

"people makes"

Example 3

let toyota = {
  drive() {
    return 'driving toyota';
 }
}
let camry = {
  wifi() {
    return 'carry';
  }
}
// Set toyota's __proto__ to camry's  __proto__'s  __proto__
Object.setPrototypeOf(camry, toyota);
console.dir(camry); //prints the camry object
console.log(camry.wifi()); // carry

Output:

[object Object] {
 drive: drive() {
    return 'driving toyota';
 },
  wifi: wifi() {
    return 'carry';
  }
}
"carry"

Next TopicJavaScript Objects

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