JavaScript in and instanceof operators Last Updated : 23 Jul, 2025 Comments Improve Suggest changes Like Article Like Report JavaScript Relational Operators are used to compare their operands and determine the relationship between them. They return a Boolean value (true or false) based on the comparison result.JavaScript in OperatorThe in-operator in JavaScript checks if a specified property exists in an object or if an element exists in an array. It returns a Boolean value. JavaScript let languages = ["HTML", "CSS", "JavaScript"]; // true (index 1 exists in the array) console.log(1 in languages); // false (index 3 doesn't exist in the array) console.log(3 in languages); Outputtrue false JavaScript const Data = { name: "Rahul", age: 21, city: "Noida" }; // true ("name" property exists in the object) console.log("name" in Data); // false ("gender" property doesn't exist in the object) console.log("address" in Data); Outputtrue falseJavaScript instanceof OperatorThe instanceof operator in JavaScript tests if an object is an instance of a particular class or constructor, returning a Boolean value. JavaScript let languages = ["HTML", "CSS", "JavaScript"]; console.log(languages instanceof Array); console.log(languages instanceof Object); console.log(languages instanceof String); console.log(languages instanceof Number); Outputtrue true false false JavaScript let myString = new String(); let myDate = new Date(); console.log(myString instanceof Object); console.log(myString instanceof Date); console.log(myString instanceof String); console.log(myDate instanceof Date); console.log(myDate instanceof Object); console.log(myDate instanceof String); Outputtrue false true true true false Comment More infoAdvertise with us V vishalkumar2204 Follow Improve Article Tags : JavaScript Web Technologies javascript-operators Explore JavaScript Tutorial 8 min read JavaScript BasicsIntroduction to JavaScript 4 min read JavaScript Versions 2 min read How to Add JavaScript in HTML Document? 3 min read JavaScript Syntax 6 min read JavaScript Output 4 min read JavaScript Comments 2 min read JS Variables & DatatypesVariables and Datatypes in JavaScript 6 min read Global and Local variables in JavaScript 4 min read JavaScript Let 6 min read JavaScript const 5 min read JavaScript Var Statement 7 min read JS OperatorsJavaScript Operators 5 min read Operator precedence in JavaScript 2 min read JavaScript Arithmetic Operators 5 min read JavaScript Assignment Operators 5 min read JavaScript Comparison Operators 5 min read JavaScript Logical Operators 5 min read JavaScript Bitwise Operators 5 min read JavaScript Ternary Operator 4 min read JavaScript Comma Operator 2 min read JavaScript Unary Operators 4 min read JavaScript in and instanceof operators 3 min read JavaScript String Operators 3 min read JS StatementsJavaScript Statements 4 min read JavaScript if-else 3 min read JavaScript switch Statement 4 min read JavaScript Break Statement 2 min read JavaScript Continue Statement 1 min read JavaScript Return Statement 4 min read JS LoopsJavaScript Loops 3 min read JavaScript For Loop 4 min read JavaScript While Loop 3 min read JavaScript For In Loop 3 min read JavaScript for...of Loop 3 min read JavaScript do...while Loop 4 min read JS Perfomance & DebuggingJavaScript | Performance 4 min read Debugging in JavaScript 4 min read JavaScript Errors Throw and Try to Catch 2 min read JS ObjectObjects in Javascript 4 min read Object Oriented Programming in JavaScript 3 min read JavaScript Objects 6 min read Creating objects in JavaScript 5 min read JavaScript JSON Objects 3 min read JavaScript Object Reference 4 min read JS FunctionFunctions in JavaScript 4 min read How to write a function in JavaScript ? 4 min read JavaScript Function Call 2 min read Different ways of writing functions in JavaScript 3 min read Difference between Methods and Functions in JavaScript 3 min read Explain the Different Function States in JavaScript 3 min read JavaScript Function Complete Reference 3 min read JS ArrayJavaScript Arrays 7 min read JavaScript Array Methods 7 min read Best-Known JavaScript Array Methods 6 min read Important Array Methods of JavaScript 7 min read JavaScript Array Reference 4 min read Like
