JavaScript Object isPrototypeOf() Method

The Object.isPrototypeOf() method in Javascript checks if an object exists in another object’s prototype chain.

Syntax:

prototypeObj.isPrototypeOf(object)

Parameters: This object accepts a single parameter.

• object: This is an object, whose prototype chain will be searched.

Return value: This method returns a boolean value.

Errors thrown: A Type Error is thrown if prototypeObj is undefined or null.

Example: This example shows the basic use of the JavaScript Object.prototype.isPrototypeOf() method.

javascript

function obj1() { }
function obj2() { }

obj1.prototype = Object.create(obj2.prototype);
const obj3 = new obj1();
console.log(obj1.prototype.isPrototypeOf(obj3));
console.log(obj2.prototype.isPrototypeOf(obj3));

Output:

true
true

Example 2: This example illustrates that C.prototype, B.prototype, A.prototype, and Object.prototype exist in the prototype chain for object c:

javascript

function A() { }
function B() { }
function C() { }

B.prototype = Object.create(A.prototype);
C.prototype = Object.create(B.prototype);

let c = new C();

console.log(C.prototype.isPrototypeOf(c));
console.log(B.prototype.isPrototypeOf(c));
console.log(A.prototype.isPrototypeOf(c));
console.log(Object.prototype.isPrototypeOf(c));

Output:

true
true
true
true

We have a complete list of Javascript Object Methods, to check those please go through the Javascript Object Complete Reference article.

Supported Browser:

• Chrome 1 and above
• Edge 12 and above
• Firefox 1 and above
• Internet Explorer-9 and above
• Opera 4 and above
• Safari 3 and above