1var array1=["A","B","C"];
2
3var array2=["1","2","3","4"];
4
5console.log(array1.flatMap(d => array2.map(v => d + v)))

1function cartesian(...args) {
2    var r = [], max = args.length-1;
3    function helper(arr, i) {
4        for (var j=0, l=args[i].length; j<l; j++) {
5            var a = arr.slice(0); // clone arr
6            a.push(args[i][j]);
7            if (i==max)
8                r.push(a);
9            else
10                helper(a, i+1);
11        }
12    }
13    helper([], 0);
14    return r;
15}
16