The Rainoce
rainoce.eu.org › javascript-for-in-loop
Understanding the JavaScript for...in Loop
April 3, 2023 - The for...in loop is a control flow statement in JavaScript that allows developers to iterate over the properties of an object.
W3Schools
w3schools.com › js › js_loop_forin.asp
JavaScript For In
The for...in loop is primarily used for objects to access their property names (keys). for (key in object) { // code block to be executed } key A variable that holds the name (key) of each property during the iterations · object The object ...
For loop in Javascript.
The condition of the loop does not dictate when the loop stops, it dictates when the loop should continue. counter == 100 says "only loop when counter is equal to 100", but you're expecting the opposite to happen. In this option, the counter should stop when the value 100 would be attributed to the counter (note the "="). No, because = doesn't check for anything. = is assignment. It's setting counter to be 100 every iteration, then evaluating to that 100 value, and 100 is truthy so the loop never ends. More on reddit.com
For loop Basic JavaScript
Good morning, I am a little confused on the logic of a for loop. If you have to find the min and max number of an array how would a for loop be used to iterate through the loop in a function? Here is example code for max number. ----- .sort() is not allowed to be used. function max(numbers) ... More on forum.freecodecamp.org
If I'm Struggling with JS Loops, Should I Even Bother?
Coding is hard, that's why not a lot of people do it. So I can assure you that this, you struggling, is going to happen again. You have to be ok with not fully understanding everything, mainly because you don't need to, to be a successful programmer. More on reddit.com
[AskJS] Difference between For Loops
Some differences include: for loops for (let i = 0; i < arr.length; i++) { // loop code } User defined loop conditions Allows breaking (and continuing) Supports await/yield for surrounding scope Standard usage for arrays gives you index only, not value Tends to be more complicated than other loops (less readable, more error prone) But also most flexible in how looping is defined for of loops for (const element of arr) { // loop code } Loops through iterables only Allows breaking (and continuing) Supports await/yield for surrounding scope Standard usage for arrays gives you value only, not index Other helpers needed for specific kinds of iteration, like array.entries() to get indices and values, or Object.keys() for going through keys of objects For arrays, loops through all values, even holes when arrays are sparse for in loops for (const key in obj) { // loop code } Loops through any value Iterates through value keys, both own and inherited (Object.keys(), by comparison, only provides own keys, not inherited) Allows breaking (and continuing) Supports await/yield for surrounding scope For arrays does not include holes when arrays are sparse (not recommended for looping through arrays) forEach loops arr.forEach(function (element, index, arr) { // loop code }) Only usable for collections that have this method (arrays, typed arrays, and some others like NodeLists from DOM API) Uses a callback function rather than looping through a code block Does not allow breaking Does not support await/yield for surrounding scope (though you can await and yield in the callback itself, it doesn't affect the looping) Gives you value, index, and collection being looped for each iteration For arrays does not include holes when arrays are sparse Often considered the most readable, especially when reusing callback functions (arr.forEach(doThing)) though can also be least performant More on reddit.com
Videos
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Learn JavaScript FOR LOOPS in 5 minutes! 🔂 - YouTube
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How to Write and Use For Loops in JavaScript | Beginner’s Guide ...
10:54
#27 For...in loop | JavaScript Full Tutorial - YouTube
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#23 JavaScript for..of and for..in Loop | JavaScript for Beginners ...
03:17
JavaScript Basics - How to use for in loops - YouTube
08:35
JavaScript Tutorial 31 - For in Loop in JavaScript | Programming ...
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Statements › for...in
for...in - JavaScript | MDN
The for...in statement iterates over all enumerable string properties of an object (ignoring properties keyed by symbols), including inherited enumerable properties.
W3Schools
w3schools.com › js › js_loop_for.asp
JavaScript for Loop
JS Examples JS HTML DOM JS HTML ... Interview Prep JS Bootcamp JS Certificate JS Reference ... For Loops can execute a block of code a number of times....
TechOnTheNet
techonthenet.com › js › for_in_loop.php
JavaScript: For-In Loop
This JavaScript tutorial explains how to use the for-in loop with syntax and examples. In JavaScript, the for-in loop is a basic control statement that allows you to loop through the properties of an object.
Reddit
reddit.com › r/learnprogramming › for loop in javascript.
r/learnprogramming on Reddit: For loop in Javascript.
November 14, 2021 -
Hello, guys. I tried to make a for loop in Javascript with the following options:
for (let counter=0;counter==100;counter++) {console.log("hello");}
In this option, the counter should stop when the value becomes 100 (note the "=="). However, here the function doesn't work (stays as "undefined").
for (let counter=0;counter=100;counter++) {console.log("hello");}
In this option, the counter should stop when the value 100 would be attributed to the counter (note the "="). However, here the function enters in an infinite loop the crashes the browser.
Something wrong w/ my rationale?
Top answer 1 of 2
3
The condition of the loop does not dictate when the loop stops, it dictates when the loop should continue. counter == 100 says "only loop when counter is equal to 100", but you're expecting the opposite to happen. In this option, the counter should stop when the value 100 would be attributed to the counter (note the "="). No, because = doesn't check for anything. = is assignment. It's setting counter to be 100 every iteration, then evaluating to that 100 value, and 100 is truthy so the loop never ends.
2 of 2
1
a==b compares a to b and returns true if they're equal. a=b assigns b to a, ensuring they're equal, so it will always be true.
SitePoint
sitepoint.com › blog › javascript › how to use the for loop in javascript
For Loop in JavaScript: How to Use the for…in Loop — SitePoint
November 7, 2024 - So, if the value variable in the for...in loop syntax structure we showed above was an array of five items, key would not be guaranteed to be 0 to 4. Some indices might precede others. Details on when this might happen is explained later in this article. In the example below, we’re looping over the following variable arr: const arr = ["JavaScript", "PHP", "Python", "Java"]; for (let key in arr) { console.log(key + ": " + arr[key]) } // Output: // "0: JavaScript" // "1: PHP" // "2: Python" // "3: Java"
Mozilla
developer.mozilla.org › en-US › docs › Web › JavaScript › Guide › Loops_and_iteration
Loops and iteration - JavaScript | MDN
A for loop repeats until a specified condition evaluates to false. The JavaScript for loop is similar to the Java and C for loop. ... The initializing expression initialization, if any, is executed. This expression usually initializes one or more loop counters, but the syntax allows an expression ...
Luis Llamas
luisllamas.es › inicio › cursos › curso javascript
for...in and for...of Loops in JavaScript
December 4, 2024 - The for...in loop is used to iterate over the enumerable properties of an object.
Programiz
programiz.com › javascript › for-loop
JavaScript for loop (with Examples)
In JavaScript, the for loop is used for iterating over a block of code a certain number of times or over the elements of an array. In this tutorial, you will learn about the JavaScript for loop with the help of examples.
GeeksforGeeks
geeksforgeeks.org › javascript › for-in-loop-in-javascript
JavaScript For In Loop - GeeksforGeeks
The for...in loop in JavaScript is used to iterate over the enumerable properties of an object.
Published January 22, 2026
GeeksforGeeks
geeksforgeeks.org › javascript › how-to-push-an-object-into-an-array-using-for-loop-in-javascript
How to Push an Object into an Array using For Loop in JavaScript ? - GeeksforGeeks
August 5, 2025 - JavaScript allows us to push an object into an array using a for-loop. This process consists of iterating over the sequence of values or indices using the for-loop and using an array manipulation method like push(), to append new elements to ...
W3Schools
w3schools.com › js › js_loops.asp
JavaScript Loops
In the following example, the code in the loop will run, over and over again, as long as a variable (i) is less than 10: while (i < 10) { text += "The number is " + i; i++; } Try it Yourself » · If you forget to increase the variable used in the condition, the loop will never end.