gistfile1.js

function collect(array, fn, scope) {
  var results = [],
      r,
      i = 0,
      index = 0,
      len = array.length;

  for (; i < len; i++) {
      r = fn.call(scope, array[i], i, array);
      if (r !== null) {
          results[index] = r;
          index++;
      }
  }

  return results;
}