The await Keyword

await pauses the continuation of an async function until a promise-like value settles. The rest of the application can keep processing events. Sequential awaits are sometimes required, but independent operations can be started together.

Reading the code: The first await unwraps "one" before the call for "two" begins. The second await unwraps "two" and the final log shows the ordered flow.

Keep the boundary clear: Avoid a loop of sequential awaits when independent requests could safely run concurrently; start the promises first when appropriate.

Save the code as await-keyword.ts. The result below was captured after compiling this exact example with strict TypeScript checking and executing the emitted JavaScript in Node.js.

TypeScript code

async function step(label: string): Promise<string> { return Promise.resolve(label); }
async function main(): Promise<void> {
  const first = await step("one");
  const second = await step("two");
  console.log(`${first} -> ${second}`);
}
main().catch(console.error);

Verified output

one -> two

Build: npx tsc --strict --target es2022 --module commonjs --lib es2022,dom,esnext.disposable await-keyword.ts; run: node await-keyword.js. The exact filename may be changed freely. When a multi-file project exists, prefer its tsconfig.json and build scripts.

The first await unwraps "one" before the call for "two" begins. The second await unwraps "two" and the final log shows the ordered flow.

The output shown above comes from the initialized values in this program. Replacing a type annotation alone does not transform a JavaScript value.

Avoid a loop of sequential awaits when independent requests could safely run concurrently; start the promises first when appropriate.

Check both the TypeScript diagnostic and the emitted JavaScript behavior. A program can compile correctly and still need runtime validation or error handling.

Call step("A") and step("B") before awaiting either and compare when the work starts.

Before running your change, write down the type you expect TypeScript to infer and the output you expect JavaScript to print. Then check both predictions.

await pauses the continuation of an async function until a promise-like value settles.

Try the practice change and re-run the exact program to test your understanding.