---
date: 2020-11-23
id: 5bccb6c2-ea64-4159-8f93-eaa16d3925b2
title: TypeScript 4.1
---

# Description

See announcement post[^1] for full changelog.

# Changes

## Flags

-   [noUncheckedIndexAccess](20201126104931-nouncheckedindexaccess)
-   [checkJs](20201127101336-checkjs) implies
    [allowJs](20201127100938-allowjs)
-   [TypeScript jsx flag](20201130085124-typescript_jsx_flag) support
    [react-jsx](20201130085253-react_jsx) and
    [react-jsxdev](20201130085317-react_jsxdev)

## Literal Types

### Literal String Type

-   [TypeScript Template Literal String
    Type](20201123101810-typescript_template_literal_string_type)

1.  Helpers

    -   [Uppercase](20201123103250-uppercase)
    -   [Lowercase](20201123103315-lowercase)
    -   [Capitalize](20201123103333-capitalize)
    -   [Uncapitalize](20201123103400-uncapitalize)

## Mapped Type

### Clauses

-   [as](20201124095453-typescript_as_clause)

## Recursive conditional types

-   [TypeScript Recursive Conditional
    Types](20201125085727-typescript_recursive_conditional_types)

# Footnotes

[^1]: <https://devblogs.microsoft.com/typescript/announcing-typescript-4-1/>
