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    Iteration in JavaScript refers to the process of repeating a set of instructions over a collection of data or until a condition is met. JavaScript provides various mechanisms for iteration, including loops, array methods, and advanced constructs like iterators and generators.

    Common Loop Constructs

    JavaScript offers several loop types for iteration:

    • for Loop: Repeats a block of code while a condition is true. It is commonly used for iterating over arrays.

    for (let i = 0; i < 5; i++) {
    console.log(i); // Outputs: 0, 1, 2, 3, 4
    }
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    • while Loop: Executes as long as a condition is true.

    let i = 0;
    while (i < 3) {
    console.log(i); // Outputs: 0, 1, 2
    i++;
    }
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    • do...while Loop: Executes at least once before checking the condition.

    let i = 0;
    do {
    console.log(i); // Outputs: 0, 1, 2
    i++;
    } while (i < 3);
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    • for...in Loop: Iterates over the enumerable properties of an object.

    const obj = { a: 1, b: 2 };
    for (let key in obj) {
    console.log(key, obj[key]); // Outputs: a 1, b 2
    }
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    • for...of Loop: Iterates over iterable objects like arrays, strings, or maps.

    What is iteration in coding?
    Iteration in coding is a way of repeating things easily. We can use the Data Type of Array, and For Loops to make it easy to repeat things like printing out things to a web page. The start of a For Loop has three parts, a loop variable, an exit condition to say when to stop looping, an iterator (a way of changing the loop variable).
    mozilla.github.io
    W3School
    https://www.w3schools.com/JS/js_array_iteration.asp
    JavaScript Array Iteration - W3Schools
  1. Mozilla Developer
    https://developer.mozilla.org › en-US › docs › Web › JavaScript › ...

    Loops and iteration - JavaScript | MDN - MDN Web Docs

    Loops offer a quick and easy way to do something repeatedly. This chapter of the JavaScript Guide introduces the different iteration statements available to JavaScript.
    Overview

    ••
    Loops offer a quick and easy way to do something repeatedly. This chapter of the JavaScript Guide introduces the different iteration statements available to JavaScript.

    for statement

    A for loop repeats until a specified condition evaluates to false. The JavaScript for loop is similar to the Java and C for loop.
    A for statement looks as follows:
    When a for loop executes, the following o…

    do...while statement

    The do...while statement repeats until a specified condition evaluates to false.
    A do...while statement looks as follows:
    statement is always executed once before the condition is checked. (To execute multiple statements, use a block stateme…

    while statement

    A while statement executes its statements as long as a specified condition evaluates to true. A while statement looks as follows:
    If the condition becomes false, statement within the loop stops executing and control passes to the statement following the loop.

  2. W3School
    https://www.w3schools.com › JS › js_array_iteration.asp

    JavaScript Array Iteration - W3Schools

    ES2019 added the Array flatMap() method to JavaScript. The flatMap() method first maps all elements of an array and then creates a new array by flattening the array.

  3. GeeksForGeeks
    https://www.geeksforgeeks.org › javascript › javascript-iterator

    JavaScript Iterator - GeeksforGeeks

    Mar 14, 2026 · A JavaScript iterator is an object that allows sequential access to elements of a collection such as arrays, strings, maps, or sets. It provides a standard way to traverse data structures …

  4. Medium
    https://medium.com › @imanthagihan › loops-and-iterations-in...

    Loops and Iterations in JavaScript: A Complete Guide - Medium

    Sep 18, 2025 · Loops and Iterations in JavaScript: A Complete Guide When writing programs, repetition is often unavoidable. Whether you’re iterating over a list of items, checking conditions multiple...

  5. JavaScript Tutorial
    https://www.javascripttutorial.net › javascript-iterator

    The Essential Guide to JavaScript Iterator

    Oct 6, 2023 · Summary: in this tutorial, you will learn about JavaScript iterators and how to use iterators to process a sequence of data more efficiently. The for loop issues

  6. DEV Community
    https://dev.to › ashishkankal

    Top 6 Iteration Methods in Javascript - DEV Community

    Jun 6, 2023 · In JavaScript, there are a variety of iteration methods that can be used to loop through arrays, objects, and other iterable data structures. These methods allow you to perform tasks such as …

  7. Web Reference
    https://webreference.com › javascript › basics › advanced...

    Advanced iteration in JavaScript explained - Web Reference

    Discover advanced techniques for iterating in JavaScript, including performance, advanced looping in arrays, and custom functions for looping over objects.

  8. Stack Overflow
    https://stackoverflow.com › questions

    How to iterate over a JavaScript object? - Stack Overflow

    Jan 17, 2013 · For object iteration we usually use a for..in loop. This structure will loop through all enumerable properties, including ones who are inherited via prototypal inheritance.

  9. FreeCodecamp
    https://www.freecodecamp.org › learn › lecture...

    How Do Loops and Iteration Work in JavaScript ...

    How Do Loops and Iteration Work in JavaScript? Loops in programming are used to repeat a block of code multiple times. An example of a loop would be when you are designing a program that needs to …

  10. PDF.js
    https://mozilla.github.io › webmaker-curriculum › Quacking...

    Javascript Basics | Javascript and Iteration - GitHub Pages

    Here we learn how to save time by using loops in Javascript. This is called Iteration in coding speak. First do the activities on your own to become familiar with it. …

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