forEach() vs map() vs filter() methods

Joe Powell — Mon, 16 Aug 2021 14:41:24 +0000

map()
The map method returns new array of elements modified or not modified, below they are not modified.

let list = [1,2,3];
let mappedList = list.map((n)=> n); 
console.log(mappedList) // [1,2,3]

forEach()
The forEach method does not return, so with forEach we can iterate through an array and push it into another array or string then return that array or string.

let list_two = [1, 2, 3, 4, 5, 6];
let itemsForEached = [];
list_two.forEach(num => itemsForEached.push(num * 0))
console.log(itemsForEached) // [0, 0, 0, 0, 0, 0]

filter()
filter returns an array filled with all the array elements that pass a test

const list = [...this.state.list];
const updatedList = list.filter(item => item.id !== id);
this.setState({ list: updatedList });
  or
const ages = [35, 37, 16, 49];
let filtered = ages.filter((age) return age >= 18 )
console.log(filtered) // [35, 37, 49]

DEV Community: Joe Powell

forEach() vs map() vs filter() methods