JavaScript Loops Explained with Examples | For Loop

Learn how loops work in JavaScript with beginner-friendly examples. This complete guide covers for loops, while loops, and practical use cases like printing messages, iterating arrays, and filtering even/odd numbers.

🔁Introduction to Loops in JavaScript

Imagine someone asks you to print "Hello world".

You’d simply write:

console.log('Hello world') 

Now let’s say your friend wants you to print "Hello world" three times:

JavaScript

console.log('Hello world')
console.log('Hello world')
console.log('Hello world')

Still manageable, right?

But what if they ask for it 100 times, or even 500 times?

Repeating console.log('Hello world') over and over is time-consuming and impractical. This is where loops come in. Loops help you perform repetitive tasks efficiently and with clean code.

✅ JavaScript for Loop Example

Here’s how you can print "Hello world" 100 times using a for loop:

JavaScript

for (let i = 0; i < 100; i++) {
  console.log('Hello world')
}

💡 When to Use Loops

Use a loop when you want to repeat a task multiple times with minimal code.

🔍 JavaScript for Loop Syntax

JavaScript

for (initialization; condition; increment / decrement) {
  // code to run in each iteration
}

Breakdown:

• Initialization: Where the loop starts (let i = 0)

• Condition: The test that decides whether to keep looping (i < 100)

• Increment/Decrement: How the counter changes after each loop (i++)

📦 Example: Printing All Values in an Array

You can use a loop to go through all elements in an array:

JavaScript

let arr = [10, 20, 44, 55, 66, 22, 88, 99, 44]

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

🔍 Example: Find All Odd Numbers in an Array

Here’s how to print only the odd numbers from an array:

JavaScript

let arr = [10, 20, 44, 55, 66, 22, 88, 99, 44]

for (let i = 0; i < arr.length; i++) {
  if (arr[i] % 2 === 1) {
    console.log(arr[i])
  }
}

🔍 Example: Find All Even Numbers in an Array

Similarly, here’s how to print only the even numbers:

JavaScript

let arr = [10, 20, 44, 55, 66, 22, 88, 99, 44]

for (let i = 0; i < arr.length; i++) {
  if (arr[i] % 2 === 0) {
    console.log(arr[i])
  }
}

⏳ Coming Soon: While Loops in JavaScript

Besides the for loop, JavaScript also provides:

• while loop

• do...while loop

These are useful when the number of repetitions is unknown at the start. We'll cover them in a future tutorial.

📘 Summary

In this tutorial, you’ve learned:

• The importance of loops in JavaScript

• How to use the for loop

• The basic syntax and structure of a loop

• Practical examples using arrays:

  • Printing each item

  • Filtering even and odd numbers

Using loops allows you to write cleaner, shorter, and more efficient code — especially for tasks that involve repetition.

📚 You will also Learn and Explore...

• JavaScript for loop tutorial

• How while Loops work in JavaScript

• Looping through arrays with for, for...of, and forEach

• JavaScript beginner tips and tricks

• Finding even and odd numbers using loops

Happy coding — and keep on looping! 🔁

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