SOURCE

function Chunk(arr = [], size = 1){
    return  arr.reduce((t, v) => (t[t.length -1].length === size ? t.push([v]) : t[t.length - 1].push(v), t),[[]]);
}
const arr = [1, 2 , 3, 4, 5];
console.log(Chunk(arr, 2));

function Difference(arr = [], oarr = []){
    return arr.reduce((t, v) =>(!oarr.includes(v) && t.push(v), t),[]);
}
const arr1 = [1, 2, 3, 4, 5];
const oarr = [2, 3, 6];
console.log(Difference(arr1, oarr));