code: function checkCacheTRBL(current, cache) {
                      if (cache === undefined)
                          return true;
                      else if (current.t !== cache.t ||
                          current.r !== cache.r ||
                          current.b !== cache.b ||
                          current.l !== cache.l)
                          return true;
                      return false;
                  }
docs: Compares two objects which have four properties and returns the result of the comparison as a boolean.
  @param current The first object with four properties.
  @param cache The second object with four properties.
  @returns {boolean} True if both objects aren't equal or some of them is undefined, false otherwise.