Question 1

How does `using` / `await using` with `Symbol.dispose` work in TypeScript 5.2+?

Accepted Answer

**Target Audience:** Developers who write cleanup code (closing connections, releasing locks, deleting temp files) and want to understand TypeScript's `using` declarations from zero.
**Difficulty:** Medium
**TypeScript version:** Checked with TypeScript 5.4.5 `--strict` (the page compiler; `using` has been supported since 5.2). The page compiles to ES2022, so it runs TypeScript's downlevel helpers. As a cross-check, both examples were also compiled to ESNext (native `using` syntax) and run in Bu

Question 2

What's new to type in TypeScript 5.5+ libs — `Array.fromAsync`, `Set` methods, `Iterator` helpers?

Accepted Answer

**Target Audience:** Developers who want to use the newest built-in JavaScript APIs from TypeScript and need to understand where the types come from and what they promise.
**Difficulty:** Medium
**TypeScript version:** The page runs TypeScript 5.4.5, whose libs have **none** of these three APIs, so the runnable examples use typed userland equivalents. The real lib signatures quoted below were read from, and checked with, **tsc 5.9.3** (`--strict --lib ESNext,DOM`) and **tsc 6.0.2**; that program

Question 3

How do you type and compose multiple disposables with `DisposableStack` and `AsyncDisposableStack`?

Accepted Answer

**Target Audience:** Developers who already know `using` and need to manage several resources together: setup that can fail half-way, objects that own other resources, and async cleanup.
**Difficulty:** Hard
**TypeScript version:** Types checked with TypeScript 5.4.5 `--strict` (`DisposableStack` and `AsyncDisposableStack` are declared in `lib.esnext.disposable`, available since 5.2). The page runtime has no built-in stacks, so Examples 1 and 2 use the built-in class when present and otherwise a

TYPESCRIPTDECODED.

Medium

How does `using` / `await using` with `Symbol.dispose` work in TypeScript 5.2+?

What's new to type in TypeScript 5.5+ libs — `Array.fromAsync`, `Set` methods, `Iterator` helpers?

Hard

How do you type and compose multiple disposables with `DisposableStack` and `AsyncDisposableStack`?