var combine = function(arr, k) {
    var result = {};
    var subresult = [];
    var n = arr.length
    var count = 0
    function combineSub(subresult){
        if(subresult.length == k){
            var subres = subresult.slice(0)
            var sub = []
            subres.forEach(item=>sub.push(arr[item]))
            var res = sub.join()
            if(result[res] == undefined){
                result[res] = sub
                count++
            }
            return;
        }
        for(var i= 0;i<n;i++){
           if(subresult.indexOf(i) ===-1){
              subresult.push(i);
              combineSub(subresult);
              subresult.pop();     
           }           
        }   
    }
    combineSub(subresult);
    return count;
}
combine([1,2,2],1)