How do different array methods in JavaScript compare?

What are the main differences between map, forEach, and filter in JavaScript?

The main differences are:

1. map creates a new array by applying a function to each element.
2. forEach executes a function on each element but does not return a new array.
3. filter creates a new array with elements that pass a test defined by a function.

Can you give me an example of how to use each of these methods?

Sure! Here are examples:

1. map:

const numbers = [1, 2, 3];
const doubled = numbers.map(num => num * 2);
// doubled: [2, 4, 6]

2. forEach:

const numbers = [1, 2, 3];
numbers.forEach(num => console.log(num));
// Logs: 1, 2, 3

3. filter:

const numbers = [1, 2, 3, 4];
const evens = numbers.filter(num => num % 2 === 0);
// evens: [2, 4]

When should I use forEach instead of map?

Use forEach when you want to perform an action on each element without needing a new array. Use map when you want to transform each element and create a new array.

Are there performance differences between these methods?

Yes, there can be performance differences. Generally, forEach is faster for simple iterations, while map and filter may be slower due to the creation of new arrays. However, the difference is often negligible for small arrays.