JavaScript Comments Last Updated : 15 Nov, 2024 Summarize Suggest changes Share Like Article Like Report 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 (//), JavaScript // A single line comment console.log("Hello Geeks!"); OutputHello Geeks! 2. Multi-line CommentsA multiline comment begins with /* and ends with */ JavaScript /* It is multi line comment. It will not be displayed upon execution of this code */ console.log("Multiline comment in javascript"); OutputMultiline comment in javascript JavaScript Comments in HTML Prerequisite : How to Add JavaScript in HTML Document?The syntax of comments remains same when we write inside HTML script tag. HTML <!DOCTYPE html> <html> <head> <title></title> </head> <body> <script> // Prinintg Hello World document.write('Hello World'); </script> </body> </html> JavaScript Comments to Prevent ExecutionWe can use // or /*...*/ to change the JavaScript code execution using comments. JavaScript Comments are used to prevent code execution and are considered suitable for testing the code. JavaScript function add() { let x = 10; let y = 20; let z = x + y; // console.log(x + y); console.log(z); } add(); Output30 Example 2: This example uses multi-line comments to prevent the execution of addition code and perform subtraction operations. JavaScript function sub() { let x = 10; let y = 20; /* let z = x + y; console.log(z); */ let z = x - y; console.log(z); } sub(); Output-10 Advertise with us Next Article Variables and Datatypes in JavaScript R riarawal99 Follow Similar Reads JavaScript Tutorial JavaScript is a programming language used to create dynamic content for websites. 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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 e 3 min read JavaScript String OperatorsJavaScript 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 StatementsJavaScript StatementsJavaScript 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-elseJavaScript if-else statement executes a block of code based on a condition. 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Example of continue to print only odd Numbers smaller than 10JavaScriptfor (let i = 0; i < 10; i++) { if (i % 2 == 0) continue; console.log(i); }Output1 3 5 7 9 How Does Continue Wo 1 min read JavaScript Return StatementThe 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.Syntaxreturn [expression]Expression Evaluation: The expression inside the brackets is evaluated and returned to the cal 4 min read JS LoopsJavaScript LoopsLoops 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 u 3 min read JavaScript For LoopJavaScript for loop is a control flow statement that allows code to be executed repeatedly based on a condition. 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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 LoopA 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 & DebuggingJavaScript | PerformanceJavaScript is a fundamental part of nearly every web application and web-based software. JavaScript’s client-side scripting capabilities can make applications more dynamic and interactive, but it also increases the chance of inefficiencies in code. 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Objects are dynamic, which means the properties can be added, modified, or deleted at runtime.There are two primary w 4 min read Introduction to Object Oriented Programming in JavaScriptAs 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 ObjectsIn 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 two 6 min read Creating objects in JavaScriptAn 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 ObjectsJSON (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 ReferenceJavaScript 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 JavaScript’s primitive data types (Number, String, Boolean, null, undefined, and symbol). It is used to st 4 min read JS FunctionFunctions in JavaScriptFunctions 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.JavaScriptfunction sum(x, y) { return x + y; } console.log(sum(6, 9)); // output: 15Function Syntax 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 CallThe 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 JavaScriptA 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 of 3 min read Difference between Methods and Functions in JavaScriptGrasping 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 JavaScriptIn 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.  In this article, we will discuss the difference between the function Person( ) { }, let person = Person ( ) 3 min read JavaScript Function Complete ReferenceA 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: Be 3 min read JS ArrayJavaScript ArraysIn 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.Array in JavaScriptWhy Use 7 min read JavaScript Array MethodsTo 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 ArrayTable of Content1. JavaScript Array length 2. JavaScript Array toString() Method3. Jav 8 min read Best-Known JavaScript Array MethodsAn 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 JavaS 6 min read Important Array Methods of JavaScriptJavaScript 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 areTable of Content1. JavaScript push() Metho 7 min read JavaScript Array ReferenceJavaScript 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 Article Tags : JavaScript Web Technologies javascript-basics Like