Last Updated : 15 Jul, 2025
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.
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.
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HTML:
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UTF-8
| Version:
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