The new `using` keyword in TypeScript 5.2

TypeScript 5.2 is out! The newest version comes with ✨Explicit Resource Management✨ and the using keyword!

Just like in C# it will now be possible to create auto-disposable resources, which means that it is no longer the consumer's responsibility to, say, close connections.

This example is copied from the TS team's blog post, which makes it quite clear how to set it up imo:

function loggy(id: string): Disposable {
  console.log(`Creating ${id}`);

  return {
    [Symbol.dispose]() {
      console.log(`Disposing ${id}`);
    },
  };
}

function func() {
  using a = loggy("a");
  using b = loggy("b");
  {
    using c = loggy("c");
    using d = loggy("d");
  }
  using e = loggy("e");
  return;

  // Unreachable.
  // Never created, never disposed.
  using f = loggy("f");
}

func();

Output:

Creating a
Creating b
Creating c
Creating d
Disposing d
Disposing c
Creating e
Disposing e
Disposing b
Disposing a

The using​​ keyword comes together with an addition to Symbol - dispose, which is how we mark an object as disposable. These are part of an ECMAScript proposal which has reached stage 3 out of 4, and will soon be available in all browsers.

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