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TypeScript 5.x Updates


TypeScript is actively maintained and updated by Microsoft. In version 5.x a lot of utility and quality of life updates were made.

This chapter covers the most popular updates to allow stricter and more flexible type safety.


As a reminder these features will only be available in 5.x+

Template Literal Types

Template Literal Types now allows us to create more precise types using template literals. We can define custom types that depend on the actual values of strings at compile time.

Example

type Color = "red" | "green" | "blue";
type HexColor<T extends Color> = `#${string}`;

// Usage:
let myColor: HexColor<"blue"> = "#0000FF";
Try it Yourself »

Index Signature Labels

Index Signature Labels allows us to label index signatures using computed property names. It helps in providing more descriptive type information when working with dynamic objects.

Example

type DynamicObject = { [key: string as `dynamic_${string}`]: string };

// Usage:
let obj: DynamicObject = { dynamic_key: "value" };
Try it Yourself »


5.x also now supports native JavaScript private fields. The TypeScript 'private' still works as discussed in Classes section.