How to make combination of elements of different arrays avoiding nested for loops?

Question

JavaScript

The question is. You need to combine arrays
Option 1
group1 = 1,2,3
group2 = 1,2,3
The output should be 11, 12, 13, 21, 22, 23, 31,32,33
Option 2
group1 = 1,2,3
group2 = 1,2,3
group3 = 1,2,3
The output should be
111, "112", "113", "121", "122", "123", "131", "132", "133", "211", "212", "213", "221", "222", "223", "231", "232", "233", "311", "312", "313", "321" ", "322", "323", "331", "332", "333"

var group1=["1","2","3"];
var group2=["1","2","3"];
var group3=["1","2","3"];
var firstDigit = "";
var secondDigit = "";
var thirdDigit = "";
var pusher = "";
var variants = [];
for(a=0; a<group1.length;a++){
  firstDigit = group1[a];
  for(b=0;b<group2.length;b++){
    secondDigit = group2[b];
    for(c=0; c<group3.length; c++){
      thirdDigit = group3[c];
      pusher = firstDigit + secondDigit + thirdDigit;
      variants.push(pusher);
    }
  }
}

But how to write a universal code if it is initially unknown how many groups there will be initially?
Groups with numbers can be either 2 or 5. And you need to combine according to the previous scheme.

Answer 1

0. Have B - an array of arrays of options.
1. Create P - an array of current positions in each array (initializing them all with zero).
2. Save (or display) the current combination - for(i) B[ i ][ P[ i ] ]
3. Loop through P from 0 to the end, find a position that can be increased, reset all that are before it.
4. If you managed to do it, go back to step 2.
This way you get no more than one nested loop.