code: function GetMethod(V, P) {
              var func = V[P];
              if (func === undefined || func === null)
                  return undefined;
              if (!IsCallable(func))
                  throw new TypeError();
              return func;
          }
docs: 7.3 Operations on Objects https://tc39.github.io/ecma262/#sec-operations-on-objects 7.3.9 GetMethod(V, P) https://tc39.github.io/ecma262/#sec-getmethod