JavaScript - Generating combinations from n arrays with m elements

Question

I\'m having trouble coming up with code to generate combinations from n number of arrays with m number of elements in them, in JavaScript. I\'ve seen similar questions about

Answer 1

var f = function(arr){
    if(typeof arr !== 'object'){
        return false;
    }

    arr = arr.filter(function(elem){ return (elem !== null); }); // remove empty elements - make sure length is correct
    var len = arr.length;

    var nextPerm = function(){ // increase the counter(s)
        var i = 0;

        while(i < len)
        {
            arr[i].counter++;

            if(arr[i].counter >= arr[i].length){
                arr[i].counter = 0;
                i++;
            }else{
                return false;
            }
        }

        return true;
    };

    var getPerm = function(){ // get the current permutation
        var perm_arr = [];

        for(var i = 0; i < len; i++)
        {
            perm_arr.push(arr[i][arr[i].counter]);
        }

        return perm_arr;
    };

    var new_arr = [];

    for(var i = 0; i < len; i++) // set up a counter property inside the arrays
    {
        arr[i].counter = 0;
    }

    while(true)
    {
        new_arr.push(getPerm()); // add current permutation to the new array

        if(nextPerm() === true){ // get next permutation, if returns true, we got them all
            break;
        }
    }

    return new_arr;
};