Arrays

console.log([1, 2 ,3, 4, 5].map(item => item*2));

let arr1 = [1, 2, 3, 4, 5, 6, 7, 8];
let arr2 = [3, 1, 8];

let arr = arr1.filter(item => {
    return arr2.indexOf(item) === -1;
});
console.log(arr);