JavaScript in and instanceof operators (original) (raw)

Last Updated : 25 Nov, 2024

**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 Operator

The 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);

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);

`

JavaScript instanceof Operator

The 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);

`

Output

true 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);

`

Output

true false true true true false

Similar Reads

JavaScript Tutorial JavaScript is a programming language used to create dynamic content for websites. It is a lightweight, cross-platform, and single-threaded programming language. JavaScript is an interpreted language that executes code line by line providing more flexibility. HTML adds Structure to a web page, CSS st 11 min read

JavaScript Basics

Introduction to JavaScript JavaScript is a versatile, dynamically typed programming language used for interactive web applications, supporting both client-side and server-side development, and integrating seamlessly with HTML, CSS, and a rich standard library. JavaScript is a single-threaded language that executes one task at 8 min read

JavaScript Versions JavaScript is a popular programming language used by developers all over the world. Itâ€™s a lightweight and easy-to-learn language that can run on both the client-side (in your browser) and the server-side (on the server). JavaScript was created in 1995 by Brendan Eich. In 1997, JavaScript became a s 2 min read

How to Add JavaScript in HTML Document? To add JavaScript in HTML document, several methods can be used. These methods include embedding JavaScript directly within the HTML file or linking an external JavaScript file. Inline JavaScriptYou can write JavaScript code directly inside the HTML element using the onclick, onmouseover, or other e 4 min read

JavaScript Syntax JavaScript syntax refers to the rules and conventions dictating how code is structured and arranged within the JavaScript programming language. This includes statements, expressions, variables, functions, operators, and control flow constructs. Syntax console.log("Basic Print method in JavaScript"); 6 min read

JavaScript Output JavaScript provides different methods to display output, such as console.log(), alert(), document.write(), and manipulating HTML elements directly. Each method has its specific use cases, whether for debugging, user notifications, or dynamically updating web content. Here we will explore various Jav 4 min read

JavaScript Comments Comments help explain code (they are not executed and hence do not have any logic implementation). We can also use them to temporarily disable parts of your code. 1. Single Line CommentsA single-line comment in JavaScript is denoted by two forward slashes (//), [GFGTABS] JavaScript // A single line 2 min read

JS Variables & Datatypes

Variables and Datatypes in JavaScript Variables and data types are foundational concepts in programming, serving as the building blocks for storing and manipulating information within a program. In JavaScript, getting a good grasp of these concepts is important for writing code that works well and is easy to understand. VariablesA varia 3 min read

Global and Local variables in JavaScript In JavaScript, understanding the difference between global and local variables is important for writing clean, maintainable, and error-free code. Variables can be declared with different scopes, affecting where and how they can be accessed. Global VariablesGlobal variables in JavaScript are those de 4 min read

JavaScript Let The let keyword is a modern way to declare variables in JavaScript and was introduced in ECMAScript 6 (ES6). Unlike var, let provides block-level scoping. This behaviour helps developers avoid unintended issues caused by variable hoisting and scope leakage that are common with var. Syntax let variab 6 min read

JavaScript const The const keyword in JavaScript is a modern way to declare variables, introduced in (ES6). It is used to declare variables whose values need to remain constant throughout the lifetime of the application. const is block-scoped, similar to let, and is useful for ensuring immutability in your code. Unl 5 min read

JavaScript Var Statement The var keyword is used to declare variables in JavaScript. It has been part of the language since its inception. When a variable is declared using var, it is function-scoped or globally-scoped, depending on where it is declared. Syntax var variable = value;It declares a variable using var, assigns 7 min read

JS Operators

JavaScript Operators JavaScript operators are symbols or keywords used to perform operations on values and variables. They are the building blocks of JavaScript expressions and can manipulate data in various ways. There are various operators supported by JavaScript. 1. JavaScript Arithmetic OperatorsArithmetic Operators 5 min read

Operator precedence in JavaScript Operator precedence refers to the priority given to operators while parsing a statement that has more than one operator performing operations in it. Operators with higher priorities are resolved first. But as one goes down the list, the priority decreases and hence their resolution. ( * ) and ( / ) 2 min read

JavaScript Arithmetic Operators JavaScript Arithmetic Operators are the operator that operate upon the numerical values and return a numerical value. Addition (+) OperatorThe addition operator takes two numerical operands and gives their numerical sum. It also concatenates two strings or numbers. [GFGTABS] JavaScript // Number + N 6 min read

JavaScript Assignment Operators Assignment operators are used to assign values to variables in JavaScript. [GFGTABS] JavaScript // Lets take some variables x = 10 y = 20 x = y // Here, x is equal to 20 console.log(x); console.log(y); [/GFGTABS]Output20 20 More Assignment OperatorsThere are so many assignment operators as shown in 6 min read

JavaScript Comparison Operators JavaScript comparison operators are essential tools for checking conditions and making decisions in your code. 1. Equality Operator (==) The Equality operator is used to compare the equality of two operands. [GFGTABS] JavaScript // Illustration of (==) operator let x = 5; let y = '5'; // Che 5 min read

JavaScript Logical Operators Logical operators in JavaScript are used to perform logical operations on values and return either true or false. These operators are commonly used in decision-making statements like if or while loops to control the flow of execution based on conditions. In JavaScript, there are basically three type 5 min read

JavaScript Bitwise Operators In JavaScript, a number is stored as a 64-bit floating-point number but bitwise operations are performed on a 32-bit binary number. To perform a bit-operation, JavaScript converts the number into a 32-bit binary number (signed) and performs the operation and converts back the result to a 64-bit numb 5 min read

JavaScript Ternary Operator The Ternary Operator in JavaScript is a shortcut for writing simple if-else statements. Itâ€™s also known as the Conditional Operator because it works based on a condition. The ternary operator allows you to quickly decide between two values depending on whether a condition is true or false. Syntax: c 5 min read

JavaScript Comma Operator JavaScript Comma Operator mainly evaluates its operands from left to right sequentially and returns the value of the rightmost operand. [GFGTABS] JavaScript let x = (1, 2, 3); console.log(x); [/GFGTABS]Output3 Here is another example to show that all expressions are actually executed. [GFGTABS] Java 2 min read

JavaScript Unary Operators JavaScript Unary Operators work on a single operand and perform various operations, like incrementing/decrementing, evaluating data type, negation of a value, etc. Unary Plus (+) OperatorThe unary plus (+) converts an operand into a number, if possible. It is commonly used to ensure numerical operat 4 min read

JavaScript in and instanceof operators 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 3 min read

JavaScript String Operators JavaScript String Operators are used to manipulate and perform operations on strings. There are two operators which are used to modify strings in JavaScript. These operators help us to join one string to another string. 1. Concatenate OperatorConcatenate Operator in JavaScript combines strings using 3 min read

JS Statements

JavaScript Statements JavaScript statements are programming instructions that a computer executes. A computer program is essentially a list of these "instructions" designed to perform tasks. In a programming language, such instructions are called statements. Types of Statements1. Variable Declarations (var, let, const)In 4 min read

JavaScript if-else JavaScript if-else statement executes a block of code based on a condition. If the condition evaluates to true, the code inside the "if" block executes; otherwise, the code inside the "else" block, if present, executes. Such control statements are used to cause the flow of execution to advance and b 4 min read

JavaScript switch Statement The JavaScript switch statement evaluates an expression and executes a block of code based on matching cases. It provides an alternative to long if-else chains, improving readability and maintainability, especially when handling multiple conditional branches. Switch Statement Example: Here, we will 5 min read

JavaScript Break Statement JavaScript break statement is used to terminate the execution of the loop or the switch statement when the condition is true. In Switch Block (To come out of the block)[GFGTABS] JavaScript const fruit = "Mango"; switch (fruit) { case "Apple": console.log("Apple is healthy. 2 min read

JavaScript Continue Statement The continue statement in JavaScript is used to break the iteration of the loop and follow with the next iteration. Example of continue to print only odd Numbers smaller than 10 [GFGTABS] JavaScript for (let i = 0; i < 10; i++) { if (i % 2 == 0) continue; console.log(i); } [/GFGTABS]Output1 3 5 7 1 min read

JavaScript Return Statement The return statement in JavaScript is used to end the execution of a function and return a value to the caller. It is used to control function behaviour and optimise code execution. Syntax return [expression]Expression Evaluation: The expression inside the brackets is evaluated and returned to the c 4 min read

JS Loops

JavaScript Loops Loops in JavaScript are used to reduce repetitive tasks by repeatedly executing a block of code as long as a specified condition is true. This makes code more concise and efficient. Suppose we want to print 'Hello World' five times. Instead of manually writing the print statement repeatedly, we can 3 min read

JavaScript For Loop JavaScript for loop is a control flow statement that allows code to be executed repeatedly based on a condition. It consists of three parts: initialization, condition, and increment/decrement. [GFGTABS] javascript // for loop begins when x=2 // and runs till x <= 4 for (let x = 2; x <= 4; x++) 5 min read

JavaScript While Loop The while loop executes a block of code as long as a specified condition is true. In JavaScript, this loop evaluates the condition before each iteration and continues running as long as the condition remains true Here's an example that prints from 1 to 5. [GFGTABS] JavaScript let count = 1; while (c 3 min read

JavaScript For In Loop The JavaScript for...in loop iterates over the properties of an object. It allows you to access each key or property name of an object. [GFGTABS] JavaScript const car = { make: "Toyota", model: "Corolla", year: 2020 }; for (let key in car) { console.log(`${key}: ${car[key]}`); } 3 min read

JavaScript for...of Loop The JavaScript for...of loop is a modern, iteration statement introduced in ECMAScript 2015 (ES6). Works for iterable objects such as arrays, strings, maps, sets, and more. It is better choice for traversing items of iterables compared to traditional for and for in loops, especially when we have bre 3 min read

JavaScript do...while Loop A do...while loop in JavaScript is a control structure where the code executes repeatedly based on a given boolean condition. It's similar to a repeating if statement. One key difference is that a do...while loop guarantees that the code block will execute at least once, regardless of whether the co 4 min read

JS Perfomance & Debugging

JavaScript | Performance JavaScript is a fundamental part of nearly every web application and web-based software. JavaScriptâ€™s client-side scripting capabilities can make applications more dynamic and interactive, but it also increases the chance of inefficiencies in code. Poorly written JavaScript can degrade user experien 4 min read

Debugging in JavaScript Debugging is the process of testing, finding, and reducing bugs (errors) in computer programs. It involves: Identifying errors (syntax, runtime, or logical errors).Using debugging tools to analyze code execution.Implementing fixes and verifying correctness.Types of Errors in JavaScriptSyntax Errors: 4 min read

JavaScript Errors Throw and Try to Catch JavaScript uses throw to create custom errors and try...catch to handle them, preventing the program from crashing. The finally block ensures that code runs after error handling, regardless of success or failure. throw: Used to create custom errors and stop code execution.try...catch: Allows you to 3 min read

JS Object

Objects in Javascript An object in JavaScript is a data structure used to store related data collections. It stores data as key-value pairs, where each key is a unique identifier for the associated value. Objects are dynamic, which means the properties can be added, modified, or deleted at runtime. There are two primary 4 min read

Introduction to Object Oriented Programming in JavaScript As JavaScript is widely used in Web Development, in this article we will explore some of the Object Oriented mechanisms supported by JavaScript to get the most out of it. Some of the common interview questions in JavaScript on OOPS include: How is Object-Oriented Programming implemented in JavaScrip 7 min read

JavaScript Objects In our previous article on Introduction to Object Oriented Programming in JavaScript we have seen all the common OOP terminology and got to know how they do or don't exist in JavaScript. In this article, objects are discussed in detail. Creating Objects: In JavaScript, Objects can be created using t 6 min read

Creating objects in JavaScript An object in JavaScript is a collection of key-value pairs, where keys are strings (properties) and values can be any data type. Objects can be created using object literals, constructors, or classes. Properties are defined with key-value pairs, and methods are functions defined within the object, e 5 min read

JavaScript JSON Objects JSON (JavaScript Object Notation) is a handy way to share data. It's easy for both people and computers to understand. In JavaScript, JSON helps organize data into simple objects. Let's explore how JSON works and why it's so useful for exchanging information. const jsonData = { "key1" : "value1", .. 3 min read

JavaScript Object Reference JavaScript Objects are the most important data type and form the building blocks for modern JavaScript. The "Object" class represents the JavaScript data types. Objects are quite different from JavaScriptâ€™s primitive data types (Number, String, Boolean, null, undefined, and symbol). It is used to st 4 min read

JS Function

Functions in JavaScript Functions in JavaScript are reusable blocks of code designed to perform specific tasks. They allow you to organize, reuse, and modularize code. It can take inputs, perform actions, and return outputs. [GFGTABS] JavaScript function sum(x, y) { return x + y; } console.log(sum(6, 9)); [/GFGTABS]Output1 5 min read

How to write a function in JavaScript ? JavaScript functions serve as reusable blocks of code that can be called from anywhere within your application. They eliminate the need to repeat the same code, promoting code reusability and modularity. By breaking down a large program into smaller, manageable functions, programmers can enhance cod 4 min read

JavaScript Function Call The call() method is a predefined JavaScript method. It can be used to invoke (call) a method with an owner object as an argument (parameter). This allows borrowing methods from other objects, executing them within a different context, overriding the default value, and passing arguments. Syntax: cal 2 min read

Different ways of writing functions in JavaScript A JavaScript function is a block of code designed to perform a specific task. Functions are only executed when they are called (or "invoked"). JavaScript provides different ways to define functions, each with its own syntax and use case. Below are the ways of writing functions in JavaScript: Table o 3 min read

Difference between Methods and Functions in JavaScript Grasping the difference between methods and functions in JavaScript is essential for developers at all levels. While both are fundamental to writing effective code, they serve different purposes and are used in various contexts. This article breaks down the key distinctions between methods and funct 3 min read

Explain the Different Function States in JavaScript In JavaScript, we can create functions in many different ways according to the need for the specific operation. For example, sometimes we need asynchronous functions or synchronous functions. Â In this article, we will discuss the difference between the function Person( ) { }, let person = Person ( ) 3 min read

JavaScript Function Complete Reference A JavaScript function is a set of statements that takes inputs, performs specific computations, and produces outputs. Essentially, a function performs tasks or computations and then returns the result to the user. Syntax: function functionName(Parameter1, Parameter2, ..) { // Function body}Example: 3 min read

JS Array

JavaScript Arrays In JavaScript, an array is an ordered list of values. Each value is called an element, and each element has a numeric position in the array, known as its index. Arrays in JavaScript are zero-indexed, meaning the first element is at index 0, the second at index 1, and so on. 1. Create Array using Lit 7 min read

JavaScript Array Methods To help you perform common tasks efficiently, JavaScript provides a wide variety of array methods. These methods allow you to add, remove, find, and transform array elements with ease. Learn More on JavaScript Array Table of Content 1. JavaScript Array length 2. JavaScript Array toString() Method3. 8 min read

Best-Known JavaScript Array Methods An array is a special variable in all programming languages used to store multiple elements. JavaScript array come with built-in methods that every developer should know how to use. These methods help in adding, removing, iterating, or manipulating data as per requirements. There are some Basic Java 7 min read

Important Array Methods of JavaScript JavaScript arrays are powerful tools for managing collections of data. They come with a wide range of built-in methods that allow developers to manipulate, transform, and interact with array elements. Some of the most important array methods in JavaScript are Table of Content 1. JavaScript push() Me 8 min read

JavaScript Array Reference JavaScript Array is used to store multiple elements in a single variable. It can hold various data types, including numbers, strings, objects, and even other arrays. It is often used when we want to store a list of elements and access them by a single variable. Syntax:const arr = ["Item1", "Item2", 4 min read