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TypeScript Weekly

Issue #187 — March 31, 2022

Functional Programming in TypeScript

How Haskell knowledge can help you write better TypeScript code in a functional programming style.

Aleksandr Pakulev

Optional Variance Annotations in TypeScript 4.7

The upcoming TypeScript 4.7 release will implement support for variance annotations which will let us mark type parameters as covariant, contravariant, or invariant using the in and out keywords. (If you find the concept of variance confusing, don’t sweat it too much! Variance annotations are definitely a niche feature of the type system.)

Anders Hejlsberg

Strong Types, Weakly Held

John goes over the Type Annotations ECMAScript proposal which adds type annotation syntax (but not type checking) to JavaScript. The proposal recently reached stage 1 of the TC39 process.

John Reilly

How Some TypeScript Utility Types Are Implemented

TypeScript provides various utility types to help us manipulate other types. A walkthrough of how some of these utility types are implemented in the type declaration files that ship with the TypeScript compiler.

Huy

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