How do the map, forEach, and reduce methods differ in JavaScript?

How do the map, forEach, and reduce methods differ in JavaScript?

The map, forEach, and reduce methods are all used to iterate over arrays, but they serve different purposes. map creates a new array by applying a function to each element, forEach executes a function on each element without returning anything, and reduce accumulates a single value from the array based on a function.

Can you give me an example of each method?

Sure! Here's a quick example:

1. map:

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

2. forEach:

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

3. reduce:

   const numbers = [1, 2, 3];
   const sum = numbers.reduce((acc, num) => acc + num, 0);
   console.log(sum); // 6
   

When should I use reduce instead of map?

You should use reduce when you want to transform an array into a single value, like a sum or an object. Use map when you want to create a new array with the same number of elements as the original, but with transformed values.

Are there performance differences between these methods?

Yes, there can be performance differences. Generally, forEach and map are faster for simple iterations, while reduce can be slower due to its accumulation process. However, the actual performance can depend on the specific use case and the size of the array.