# 🔁 Transform Like a Pro: Mastering `.map()` and Method Chaining in JavaScript

This content originally appeared on DEV Community and was authored by Aman kumar

When working with arrays, you don’t just want to loop through them — sometimes you want to transform them. That’s where .map() becomes your best friend.

Today, we’ll explore how .map() works and take it further with method chaining — a pattern that makes your code both powerful and readable.

What is .map()?

.map() is a method in JavaScript that creates a new array by applying a function to every element in the original array.

Let’s take an example:

const myNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

const plusTen = myNumbers.map((num) => num + 10);

console.log(plusTen);

Output:

[11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

The original array stays unchanged. .map() returns a new transformed array.

With Explicit return (Block Syntax)

const plusTen = myNumbers.map((num) => {
  return num + 10;
});

You can use curly braces and return when your logic needs more space, but for simple expressions, inline (arrow) form is shorter and cleaner.

Method Chaining: map() + map() + filter()

Here’s where things get exciting. You can chain multiple array methods together to build transformations in one go.

const myNums = myNumbers
  .map((num) => num * 10)   // Step 1: Multiply each number by 10
  .map((num) => num + 1)    // Step 2: Add 1 to each result
  .filter((num) => num >= 40); // Step 3: Keep only values >= 40

console.log(myNums);

Output:

[41, 51, 61, 71, 81, 91]

Let’s break it down:

• 1 * 10 = 10 → 10 + 1 = 11 → rejected (less than 40)
• 4 * 10 = 40 → 40 + 1 = 41 → kept
• …
• 9 * 10 = 90 → 90 + 1 = 91 → kept

Chaining makes your code more declarative, readable, and efficient. It’s like passing your array through a pipeline of transformations.

When to Use .map()

Final Takeaway

• Use .map() when you want to transform each item in an array.
• Combine .map(), .filter(), and others for powerful, clean operations.
• Prefer method chaining for concise and readable code.

This content originally appeared on DEV Community and was authored by Aman kumar