Simple array intersect function in coffeescript

array_intersect.coffee

arrayIntersect_ = (arg1, arg2) ->
    retVal = []
    hashMap = {}
    
    for l in arg1
        hashMap[l] = 1
        
    for l in arg2
        if hashMap[l] and ((hashMap[l] += 1) == 2)
            retVal.push(l)
            
    return retVal

arrayIntersect = (arg1, arg2) ->
    ## init iterate menggunakan list yang lebih kecil
    if arg1.length <= arg2.length
        return arrayIntersect_(arg1, arg2)
    return arrayIntersect_(arg2, arg1)

## example
arrayIntersect(['a', 'b'], ['b'])


// compiled from coffeescript into javacript
var arrayIntersect, arrayIntersect_;

arrayIntersect_ = function(arg1, arg2) {
  var hashMap, l, retVal, _i, _j, _len, _len2;
  retVal = [];
  hashMap = {};
  for (_i = 0, _len = arg1.length; _i < _len; _i++) {
    l = arg1[_i];
    hashMap[l] = 1;
  }
  for (_j = 0, _len2 = arg2.length; _j < _len2; _j++) {
    l = arg2[_j];
    if (hashMap[l] && ((hashMap[l] += 1) === 2)) retVal.push(l);
  }
  return retVal;
};

arrayIntersect = function(arg1, arg2) {
  if (arg1.length <= arg2.length) return arrayIntersect_(arg1, arg2);
  return arrayIntersect_(arg2, arg1);
};

arrayIntersect(['a', 'b'], ['b']);