Differences between: forEach(), filter() and map() methods and its case uses.

#javascript #webdev #programming

Here are the use cases for forEach(), filter() and map()in JavaScript:

forEach()

Use forEach() when you need to execute a function on each element of an array without returning a new array.
it is typically used for side effects, such as modifying each element, logging, or updating external variables

const nums = [1,2,3,4];
nums.forEach((num) => {
    console.log(num * 2); // Side effect: logging each element multiplied by 2
});

filter()

Use map() when you need to create a new array containing only the elements that meet a certain condition.
It returns a new array with all the elements that pass the test implemented by the provided function

const nums = [1, 2, 3, 4];
const evenNums = nums.filter((num) => num % 2 === 0);
console.log(evenNums); // Output: [2, 4]

map()

Use map() when you need to create a new array by transforming each element of the original array.
It returns a new array with the results of calling a provided function on every element in the calling array.

const nums = [1, 2, 3, 4];
const halfNums = nums.map((num) => num / 2);
console.log(halfNums); // Output: [0.5, 1, 1.5, 2]

The performance differences between forEach(),filter(), and map() in JavaScript are generally minimal for most use cases, but there are some key points to consider:

forEach():

Performance: forEach() is typically the fastest of the three because it does not create a new array. It simply iterates over the existing array and performs the specified operation
Use Case: Best used for operations that do not required a new array, such as logging, modifying elements in place, or performing side effects.
Summary: Fastest for side effects without creating a new array.

filter():

Performance: creates a new array containing only the elements that pass the test implemented by the provided function. This involves iterating over the array and potentially allocating memory for the new array, which can be slightly slower than forEach().
Use Case: Best used when you need to extract a subset of elements from an array based on a condition.
Summary: Slightly slower due to creating a new array with elements that pass a test

map():

Performance: creates a new array with the result of calling a provided function on every element in the original array. This also involves iterating over the array, which can be slightly slower than forEach().
Use Case: Best used when you need to transform each element of an array into a new form.
Summary: Slightly slower due to creating a new array with transformed elements.