JavaScript Loops Explained with Examples


Loops in JavaScript are used to repeat a block of code multiple times—until a certain condition is false. They are essential for iterating over arrays, objects, and performing repetitive tasks.



1. for Loop – Best for known iteration count


Syntax:

for (initialization; condition; increment) {
  // code block
}


Example:

for (let i = 1; i <= 3; i++) {
  console.log("Count: " + i);
}

Output

Count: 1 Count: 2 Count: 3


2. while Loop – Runs while the condition is true


Example:

let i = 1;
while (i <= 3) {
  console.log("While loop count: " + i);
  i++;
}

Output

While loop count: 1
While loop count: 2
While loop count: 3


3. do...while Loop – Runs at least once, then checks condition


Example:

let i = 1;
do {
  console.log("Do While count: " + i);
  i++;
} while (i <= 3);

Output

Do While count: 1
Do While count: 2
Do While count: 3


4. for...of Loop – Loops over iterables like arrays


Example:

let fruits = ["Apple", "Banana", "Cherry"];

for (let fruit of fruits) {
  console.log(fruit);
}

Output

Apple
Banana
Cherry


5. for...in Loop – Loops over object keys


Example:

let person = { name: "Alice", age: 25 };

for (let key in person) {
  console.log(key + ": " + person[key]);
}

Output

name: Alice
age: 25

Summary Table – JavaScript Loops

Loop Type Use Case Iterates Over
for Known number of iterations Counters/indexes
while Unknown count, condition controlled Conditions
do...while Must run at least once Conditions
for...of Iterate over arrays/strings Iterables (Array, Set)
for...in Iterate over object properties Object keys