Loops in JavaScript repeat a block of code until a specified condition is met. They help automate repetitive tasks and reduce code duplication.

 

for Loop

It is used when the number of iterations is known in advance.

var numbers = [1, 3, 5, 3, 7, 8, 9];

	for(let i =0; i< numbers.length; i++)
	{
		console.log(numbers[i]);
	}

Output:

1
3
5
3
7
8
9

while Loop

This is used when the number of iterations is not known in advance (run when the condition is true).

 

Example:

var numbers = [1, 3, 5, 3, 7, 8, 9];
let i =0;
while(i <=numbers.length)
{
 console.log(numbers[i]);
 i++;
}

 

Output:

1
3
5
3
7
8
9

do...while Loop

This ensures that the code is executed at least once, even if the condition is false.

Example:

var numbers = [1, 3, 5, 3, 7, 8, 9];
let i = 0;
do {
    console.log(numbers[i]);
    i++;
} 
while (i <= numbers.length);

Output:

1
3
5
3
7
8
9

for...in Loop (Used for Objects)

Iterates over the keys (properties) of an object.

Example:

let person = { name: "John", age: 30, city: "New York" };
for (let key in person) {
    console.log(key + ": " + person[key]);
}

Output:

name: John
age: 30
city: New York

 

for...of Loop (Used for Arrays & Iterables)

Iterates over the values ​​in an array or iterable object.

Example:

let numbers = [10, 20, 30, 40];
for (let num of numbers) {
    console.log(num);
}

Output:

10
20
30
40

Loop Control Statements

• Break → Exits the loop immediately.
• Continue → Skips the current iteration and moves on to the next one.

 

Use break

Example:

for (let i = 1; i <= 5; i++) {
    if (i === 3) {
        break;  // Stops at 3
    }
    console.log(i);
}

Output:

1
2

 

Use continue

for (let i = 1; i <= 5; i++) {
    if (i === 3) {
        continue;  // Skips 3
    }
    console.log(i);
}

Output:

1
2
4
5

 

I hope you understand clearly all the types of javascript loop.

Thanks.

 

Also, read: LINQ to SQL LIKE operator with C#