Advanced Concatenator (GEJS)

concatenator2.js

// This fails with ["a,,", "b"] Do you know how to fix it? We'll see how to in class
var concatenator = function(arr, optSeparator) {
  if(!arr || typeof(arr.join) != 'function')
    return;
  var separator = typeof(optSeparator) == 'string' ? optSeparator : ',';
  var r = arr.join();
  if(separator != ',')
    r = r.replace(/,/g, separator);
  return r;
}