TypeScript 5: A look at the major changes

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In this article, we’ll take a look at some of the major changes in TypeScript 5.

TypeScript 5 was released earlier this month. The latest version features numerous improvements to make the language smaller, simpler, and faster.

Here are the biggest changes in the latest release:

Variadic tuple types

Variadic tuple types allow developers to define tuple types with a variable number of elements. 

In previous versions of TypeScript, the number of elements in a tuple was fixed, making it difficult to work with functions that have a varying number of arguments.

With variadic tuple types, developers can now define a tuple type with a spread element, which can take any number of arguments.

Key remapping in mapped types

Mapped types in TypeScript allow developers to create new types by mapping over an existing type.

In TypeScript 5, mapped types now support key remapping, which allows developers to rename keys when creating a new type. This is especially useful when working with third-party libraries that use different naming conventions.

Smarter type inference

TypeScript 5 introduces several improvements to its type inference system, making it smarter and more accurate. For example, TypeScript 5 can now infer types from destructured arrays and objects, making it easier to work with complex data structures.

Additionally, TypeScript 5 can now infer types from default function arguments—making it easier to write reusable code.

Abstract construct signatures

TypeScript 5 introduces a new feature called abstract construct signatures, which allows developers to define abstract classes with a constructor signature. This makes it easier to create abstract classes that can be extended by other classes, as it provides a clear definition of the class’ constructor.

Stricter class property initialisation

TypeScript 5 introduces stricter rules for class property initialisation.

In previous versions of TypeScript, it was possible to declare a class property without initialising it, which could lead to runtime errors.

With TypeScript 5, all class properties must be initialised either in the constructor or with a default value.

Improved error messages

TypeScript 5 comes with several improvements to its error messages, making it easier to diagnose and fix issues in your code.

For example, TypeScript 5 now provides more detailed error messages for type mismatches, making it easier to identify where the error occurred.

Faster compilation

TypeScript 5 introduces several performance improvements, making compilation times faster. 

This is especially noticeable when working with large projects, as TypeScript 5 can now process files in parallel, reducing overall compile times.

To get started with TypeScript 5, you can get it through NuGet or use npm with the command: npm install -D typescript

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