Loops in JavaScript

Hey everyone! Today, we will explore loops in JavaScript, a key concept for automating repetitive tasks. Whether you're just starting or need a quick refresher, this guide will help you understand how loops work in JavaScript. Let's get started!

• Loops allow you to execute a block of code repeatedly while a specified condition is true.

• JavaScript provides several types of loops, such as for, while, and do-while loops.

1. For Loop

The for loop is the most commonly used loop in JavaScript. It repeats a block of code for a set number of times.

for (let i = 0; i < 5; i++) {              // Loop from 0 to 4  
    console.log(i);                       // Print the current value of 'i'  
}  

2. For-In Loop

The for-in loop is used to iterate over the properties of an object.

let person = {name: 'John', age: 30};      // Object with 'name' and 'age' properties  
for (let key in person) {                  // Iterate over each property in the 'person' object  
    console.log(key + ': ' + person[key]); // Print the property and its value  
}  

3. For-Of Loop

The for-of loop is used to iterate over iterable objects like arrays or strings.

let numbers = [1, 2, 3, 4, 5];            // Array of numbers  
for (let num of numbers) {                // Iterate over each number in the 'numbers' array  
    console.log(num);                     // Print the current number  
}  

4. While Loop

The while loop executes a block of code as long as the specified condition is true.

let count = 0;                            // Initialize 'count' to 0  
while (count < 5) {                       // Continue looping while 'count' is less than 5  
    console.log(count);                   // Print the current value of 'count'  
    count++;                              // Increment 'count' by 1  
}  

5. Do-While Loop

The do-while loop is similar to the while loop but ensures the code is executed at least once before checking the condition.

let count = 0;                            // Initialize 'count' to 0  
do {                                       // Execute the loop body at least once  
    console.log(count);                   // Print the current value of 'count'  
    count++;                              // Increment 'count' by 1  
} while (count < 5);                      // Continue looping while 'count' is less than 5  

6. Break Statement

The break statement is used to exit a loop prematurely.

for (let i = 0; i < 10; i++) {            // Loop from 0 to 9  
    if (i === 5) {                        // Check if 'i' equals 5  
        break;                            // Exit the loop when 'i' is 5  
    }  
    console.log(i);                       // Print numbers from 0 to 4  
}  

7. Continue Statement

The continue statement skips the current iteration of the loop and moves to the next iteration.

for (let i = 0; i < 5; i++) {             // Loop from 0 to 4  
    if (i === 3) {                        // Check if 'i' equals 3  
        continue;                         // Skip the iteration when 'i' is 3  
    }  
    console.log(i);                       // Print numbers except 3  
}  

8. Nested Loops

In JavaScript, you can use loops inside other loops. These are called nested loops and are useful for iterating over multi-dimensional arrays.

for (let i = 1; i <= 3; i++) {            // Outer loop from 1 to 3  
    for (let j = 1; j <= 2; j++) {        // Inner loop from 1 to 2  
        console.log(`i: ${i}, j: ${j}`);  // Print the values of 'i' and 'j'  
    }  
}  

9. Loop Control Statements

Loop control statements allow you to control the flow of loops. Here are some common loop control statements in JavaScript:

• break: Exits the loop immediately.
• continue: Skips the current iteration and moves to the next one.
• return: Exits the loop and the enclosing function.

10. Infinite Loops

An infinite loop is a loop that runs indefinitely. It occurs when the loop condition is always true or the loop lacks an exit condition.

while (true) {                            // Infinite loop  
    console.log('This is an infinite loop!');  
}  

Conclusion

Loops are essential for automating repetitive tasks in JavaScript. By using loops effectively, you can iterate over data structures, perform calculations, and execute code based on conditions. Practice writing loops to enhance your programming skills and build efficient applications.