let arr1 = [1, 5, 4, 2];
let arr2 = [1, 91, 4, 1, 3];
//let result = arr1.concat(arr2).sort((a, b) => a - b );
let arr3 = [];
for(let i=0; i < arr1.length; i++){
        if (arr2.includes(arr1[i])) {
            arr3.push(arr1[i]);
        }
    }