Loops: while and for

JavaScript Loops: while and for

Loops are used to execute a block of code multiple times until a condition is met.

1️⃣ while Loop

Repeats while a condition is true.

Syntax

while (condition) {
    // Code to execute
}

Example: Print numbers 1 to 5

let i = 1;

while (i <= 5) {
    console.log(i);
    i++; // Increment `i` to avoid infinite loop
}

📌 Output:

1
2
3
4
5

🔹 Explanation:

• Starts at i = 1
• Runs until i <= 5 becomes false
• i++ increases i after each loop

2️⃣ do...while Loop

Executes at least once, then repeats while the condition is true.

Syntax

do {
    // Code to execute
} while (condition);

Example: Run at least once

let num = 10;

do {
    console.log(num);
    num++;
} while (num < 5);

📌 Output:

10

🔹 Explanation:

• Runs once, even though num < 5 is false
• Useful when code should execute at least once

3️⃣ for Loop

Repeats a fixed number of times.

Syntax

for (initialization; condition; increment) {
    // Code to execute
}

🔹 Breakdown:

• initialization → Start the loop
• condition → Run while true
• increment → Change variable each loop

Example: Print numbers 1 to 5

for (let i = 1; i <= 5; i++) {
    console.log(i);
}

📌 Output:

1
2
3
4
5

4️⃣ for vs. while

Feature	while Loop	for Loop
Use Case	When the number of iterations is unknown	When the number of iterations is known
Structure	Condition only	Initialization, condition, increment in one line
Example	while (x < 10) {...}	for (let i = 0; i < 10; i++) {...}

5️⃣ for...of Loop (For Arrays & Iterables)

Loops through values in an array.

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

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

📌 Output:

Apple
Banana
Cherry

6️⃣ for...in Loop (For Objects)

Loops through keys in an object.

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

7️⃣ Loop Control: break & continue

break → Stop the loop completely

for (let i = 1; i <= 5; i++) {
    if (i === 3) break; // Stop when `i` is 3
    console.log(i);
}

📌 Output:

1
2

continue → Skip current iteration

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

📌 Output:

1
2
4
5

🎯 Summary

✅ while → Use when iterations are unknown
✅ do...while → Runs at least once
✅ for → Use when iterations are known
✅ for...of → Loop over arrays & iterables
✅ for...in → Loop over object properties
✅ break → Stop loop | continue → Skip iteration

🚀 Now you're ready to use loops in JavaScript! Let me know if you need help. 😊