code: function checkCacheDouble(current, cache, prop1, prop2, force) {
                      if (force === true)
                          return force;
                      if (prop2 === undefined && force === undefined) {
                          if (prop1 === true)
                              return prop1;
                          else
                              prop1 = undefined;
                      }
                      prop1 = prop1 === undefined ? 'w' : prop1;
                      prop2 = prop2 === undefined ? 'h' : prop2;
                      if (cache === undefined)
                          return true;
                      else if (current[prop1] !== cache[prop1] || current[prop2] !== cache[prop2])
                          return true;
                      return false;
                  }
docs: Compares two objects with two properties and returns the result of the comparison as a boolean.
  @param current The first object which shall be compared.
  @param cache The second object which shall be compared.
  @param prop1 The name of the first property of the objects which shall be compared.
  @param prop2 The name of the second property of the objects which shall be compared.
  @param force If true the returned value is always true.
  @returns {boolean} True if both variables aren't equal or some of them is undefined or when the force parameter is true, false otherwise.