creates a new array with the result of calling the provided function for each value in the array
const list = [1, 2, 3, 4] const squares = list.map(a => a * a) console.log(squares) // [1, 4, 9, 16]
creates a new array including only the values where the function returns a truthy value when called with the value
const list = [1, 2, 3, 4, 5] const evenNumbers = list.filter( number => number % 2 === 0 ) console.log(evenNumbers) // [2, 4]
incrementally build a value while iterating over the values in the array, passing the result of the last step into the next
const list = [1, 2, 3, 4] const sum = list.reduce( (res, value) => res + value, 0 ) console.log(sum) // 10
find the first element in an array that the function returns a truthy value for
const animals = ['š¶', 'š', 'š±'] const cat = animals.find( animal => animal === 'š±' ) console.log(cat) // 'š±'
find the index of the first element in an array that the function returns a truthy value for
const animals = ['š¶', 'š', 'š±'] const catIndex = animals.findIndex( animal => animal === 'š±' ) console.log(catIndex) // 2
By Kristoffer Brabrand
Senior developer @ Behalf
