TypeScript 4.1 beta brings template literal types
TypeScript 4.1, a planned upgrade to Microsoft’s popular open source language that adds types to JavaScript, is now available as a beta release, featuring template literal types and a multitude of other improvements.
The template literal type has the same syntax as template literal strings in JavaScript except it is used in type positions. When used with concrete literal types, a new string literal type is produced by concatenating the contents.