Snippet

Deterministic Resource Cleanup with `await using`

`await using` (TC39 Explicit Resource Management, supported since TypeScript 5.2) binds an async-disposable to a block scope and invokes its `Symbol.asyncDispose` method when the scope exits — even when an exception escapes. This eliminates the try/finally boilerplate that traditionally protected connection pools, file handles and locks, and guarantees ordered teardown across multiple resources in LIFO order. Combined with `AsyncDisposable`, you get RAII semantics that survive async control flow.

snippet.ts

typescript

class DbConnection implements AsyncDisposable {
  constructor(public readonly id: string) {}
  async query(sql: string): Promise<unknown[]> { return []; }
  async [Symbol.asyncDispose](): Promise<void> {
    console.log(`closing ${this.id}`);
  }
}
 
async function fetchUsers(): Promise<unknown[]> {
  await using conn = new DbConnection("main");
  return conn.query("SELECT * FROM users");
}

Breakdown

class DbConnection implements AsyncDisposable {

Declares conformance to the AsyncDisposable contract.

async [Symbol.asyncDispose](): Promise<void> {

Cleanup hook the runtime awaits when the binding leaves scope.

await using conn = new DbConnection("main");

Binds conn for the rest of the block; disposal runs even on throw.

return conn.query("SELECT * FROM users");

The pending promise is awaited before disposal because of await using.

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Deterministic Resource Cleanup with `await using`

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