Example : Combining type Color = "red" | "blue" and type Size = "small" | "large" into $Color-$Size results in four distinct types: "red-small" , "red-large" , "blue-small" , and "blue-large" . Core Features and Utility Types
: If a union of types is used within the template, TypeScript generates every possible combination of those strings. TypeScript 4.1 beta brings template literal types
Template literal types bring the syntax of JavaScript's template strings (using backticks and ${} ) into type positions. While standard string literal types define a variable as holding a specific, fixed string, template literal types allow for the of new string types by concatenating existing ones. Key Syntax and Composition Example : Combining type Color = "red" |
This "paper" explores the introduction and application of template literal types, a feature introduced in the TypeScript 4.1 beta that expanded the language's ability to manipulate strings within the type system. Overview of Template Literal Types While standard string literal types define a variable
: When combined with conditional types and the infer keyword, template literal types can act as a simple parser, breaking down complex strings into their constituent parts for deep type inspection. Conclusion Documentation - Template Literal Types - TypeScript
: Developers can now enforce specific patterns, such as validating IPv4 addresses (e.g., $number.$number.$number.$number ) directly at the type level.
: Combining a literal type with a template produces a single, specific string type.
