JavaScript Object isPrototypeOf() Method Last Updated : 15 Jul, 2025 Comments Improve Suggest changes Like Article Like Report 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 aboveEdge 12 and aboveFirefox 1 and aboveInternet Explorer-9 and aboveOpera 4 and aboveSafari 3 and above Comment More info T thacker_shahid Follow Improve Article Tags : JavaScript Web Technologies javascript-object JavaScript-Methods Explore JavaScript BasicsIntroduction to JavaScript4 min readVariables and Datatypes in JavaScript6 min readJavaScript Operators5 min readControl Statements in JavaScript4 min readArray & StringJavaScript Arrays7 min readJavaScript Array Methods7 min readJavaScript Strings6 min readJavaScript String Methods9 min readFunction & ObjectFunctions in JavaScript5 min readJavaScript Function Expression3 min readFunction Overloading in JavaScript4 min readObjects in Javascript4 min readJavaScript Object Constructors4 min readOOPObject Oriented Programming in JavaScript3 min readClasses and Objects in JavaScript4 min readWhat Are Access Modifiers In JavaScript ?5 min readJavaScript Constructor Method7 min readAsynchronous JavaScriptAsynchronous JavaScript2 min readJavaScript Callbacks4 min readJavaScript Promise4 min readEvent Loop in JavaScript4 min readAsync and Await in JavaScript2 min readException HandlingJavascript Error and Exceptional Handling6 min readJavaScript Errors Throw and Try to Catch2 min readHow to create custom errors in JavaScript ?2 min readJavaScript TypeError - Invalid Array.prototype.sort argument1 min readDOMHTML DOM (Document Object Model)9 min readHow to select DOM Elements in JavaScript ?3 min readJavaScript Custom Events4 min readJavaScript addEventListener() with Examples9 min readAdvanced TopicsClosure in JavaScript4 min readJavaScript Hoisting6 min readJavascript Scope3 min readJavaScript Higher Order Functions7 min readDebugging in JavaScript4 min read Like