JavaScript For Loop

JavaScript For Loop – Looping Through Code

The for loop in JavaScript is used to repeat a block of code a certain number of times.

1. Syntax of for Loop:

for (initialization; condition; increment/decrement) {
    // Code to be executed in each iteration
}

Explanation:

• Initialization: This part runs once before the loop starts. It is typically used to initialize a counter variable.
• Condition: This expression is evaluated before each loop iteration. The loop runs as long as this condition evaluates to true.
• Increment/Decrement: This expression updates the loop counter after each iteration.

2. Example of a Simple for Loop:

for (let i = 0; i < 5; i++) {
    console.log("Iteration number: " + i);
}

Explanation:

• The loop starts with i = 0.
• The loop runs as long as i < 5.
• After each iteration, i is incremented by 1.

Output:

Iteration number: 0
Iteration number: 1
Iteration number: 2
Iteration number: 3
Iteration number: 4

3. Using for Loop to Iterate Over an Array:

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

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

Explanation:

• The loop iterates through the fruits array.
• fruits.length gives the number of elements in the array, ensuring the loop iterates over each element.

Output:

Apple
Banana
Cherry

4. Using for Loop with Decrement:

for (let i = 5; i > 0; i--) {
    console.log("Countdown: " + i);
}

xplanation:

• The loop starts with i = 5 and decrements i by 1 in each iteration until i > 0 is false.

Output:

Countdown: 5
Countdown: 4
Countdown: 3
Countdown: 2
Countdown: 1

5. Nested for Loops:

A nested for loop is a loop inside another loop. It is often used for working with multi-dimensional arrays or grids.

for (let i = 1; i <= 3; i++) {
    for (let j = 1; j <= 3; j++) {
        console.log(`i: ${i}, j: ${j}`);
    }
}

Explanation:

• The outer loop runs 3 times (i from 1 to 3).
• For each iteration of the outer loop, the inner loop runs 3 times (j from 1 to 3).

Output:

i: 1, j: 1
i: 1, j: 2
i: 1, j: 3
i: 2, j: 1
i: 2, j: 2
i: 2, j: 3
i: 3, j: 1
i: 3, j: 2
i: 3, j: 3

6. Skipping and Breaking Loops:

Using break Statement:

The break statement exits the loop immediately.

for (let i = 0; i < 10; i++) {
    if (i === 5) {
        break;
    }
    console.log(i);
}

Output:

0
1
2
3
4

Using continue Statement:

The continue statement skips the current iteration and proceeds with the next one.

for (let i = 0; i < 10; i++) {
    if (i === 5) {
        continue;
    }
    console.log(i);
}

Output:

0
1
2
3
4
6
7
8
9

Conclusion:

• The for loop is a powerful and versatile way to iterate over items or perform repeated tasks.
• It offers full control over the iteration process through initialization, condition checking, and increment/decrement expressions.
• Using break and continue helps manage flow control within loops effectively.