Description See announcement post1 for full changelog. Changes Flags noUncheckedIndexAccess checkJs implies allowJs TypeScript jsx flag support react-jsx and react-jsxdev Literal Types Literal String Type TypeScript Template Literal String Type Helpers Uppercase Lowercase Capitalize Uncapitalize Mapped Type Clauses TypeScript as Clause Recursive conditional types TypeScript Recursive Conditional Types Footnotes Footnotes https://devblogs.microsoft.com/typescript/announcing-typescript-4-1/ ↩