code: function compact(array) {
    const aResult = [];
    for (let idx = 0, len = array.length; idx < len; idx++) {
      if (array[idx]) { aResult.push(array[idx]); }
    }
    return aResult;
  }
docs: returns a copy of the array with all false values removed
  
  @param {Array} array - array
  @param {Function} fn - predicate function for cluster rule