1const array = [1, 2, 3];array.forEach(function(elem, index, array) { array[index] = elem * 2;});console.log(array); // [2,4,6]
1const array = [1,2,3,4,5];const evenNumbers = array.filter(function(elem) { // expressions that return 'true' are retained return elem % 2 == 0;});