Compile typescript without transpiling async functions

Question

Is there a way to use the TypeScript compiler only to remove type annotations, but not transpiling async functions? Something like a { target: 'esInfinite' } option? The reason is: There are browsers that already support async functions, so I wish to have a build target where those functions are not affected.

example input:

async function foo(a : number) : Promise<void> {}

example output:

async function foo(a) {}

Audit

There's a pull request to add support for ES2017, but until that lands, not as far as I am aware. – Nabala

Answer 1

In your tsconfig.json, change your target to ES2017, then it will preserve the async/await.

{
  "compilerOptions": {
    .....
    "target": "ES2017",
    .....
  }
}

DO make sure your run-time supports it natively!!!

PS: as of Apr 2018, AWS Lambda now supports Nodejs 8. You should be able to use the above config for it.

Histogen

Answer 2

This feature was already requested here. Targeting es2016 and es2017 should be available in the Community milestone and in TypeScript 2.1.

Audit

We are now at TypeScript 4.3 and setting "target" to "es2017" will preserve async / await statements using "target" with "es2016" will output a polyfill using var __awaiter. – Cornetcy