Day-37 Today I Learned: JavaScript Array Iteration Methods

JavaScript arrays are more powerful than they seem at first glance. Today, I dove into five powerful methods that make working with arrays clean, expressive, and efficient. Here's a quick summary of what I learned about forEach, map, filter, reduce, and find.

1. forEach() – Just Loop Through It

forEach is used to run a function once for each item in the array.

const fruits = ['apple', 'banana', 'cherry'];

fruits.forEach((fruit, index) => {
  console.log(`${index + 1}. ${fruit}`);
});

Use case: When you just want to iterate and do something — like logging, updating the DOM, etc.
Note: It doesn't return anything (always undefined).

2. map() – Transform Every Element

map creates a new array by applying a function to every item.

const numbers = [1, 2, 3];
const squared = numbers.map(num => num * num);

console.log(squared); // [1, 4, 9]

Use case: When you want to transform data without changing the original array.

3. filter() – Keep What You Need

filter returns a new array containing only the elements that match a condition.

const ages = [12, 18, 21, 16, 30];
const adults = ages.filter(age => age >= 18);

console.log(adults); // [18, 21, 30]

Use case: When you want to exclude certain elements based on a condition.

4. reduce() – Boil It Down to One Value

reduce is powerful and flexible. It takes a function and reduces the array to a single value.

const numbers = [10, 20, 30];
const total = numbers.reduce((acc, curr) => acc + curr, 0);

console.log(total); // 60

Use case: When you want to compute a single value like sum, average, or even build a new object or array.

5. find() – Stop at the First Match

find returns the first element that matches a condition.

const users = [
  { id: 1, name: 'Ram' },
  { id: 2, name: 'Shyam' },
];

const user = users.find(user => user.id === 2);

console.log(user); // { id: 2, name: 'Shyam' }

Use case: When you're looking for one specific item in an array.

Quick Summary

Final Thoughts

Learning these array methods helped me understand how expressive and functional JavaScript can be. They make code more readable, concise, and easier to maintain.