Using async requires async function, but my function is async

Question

I\'m adapting a library that uses callback to use Promises. It\'s working when I use then(), but it doesn\'t work when I use await.

Answer 1

You may not need async await abstraction really. Why don't you just simply promisify dbc.solve() function with a promisifier like;

function promisify(f){
  return data => new Promise((v,x) => f(data, (err, id, sol) => err ? x(err) : v({i:id, s:solution})));
}

You will have a promisified version of your dbc.solve() and if it doesn't fire an error you will be returned with an object like {i:id, s: solution} at it's then stage.

Answer 2

The await operator can only be used in an async function.

Answer 3

SyntaxError: await is only valid in async function - just like the error tells you, you may only use await inside a function which is marked as async. So you cannot use the await keyword anywhere else.

https://basarat.gitbooks.io/typescript/docs/async-await.html

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-1-7.html

examples:

function test() {
  await myOtherFunction() // NOT working
}

async function test() {
  await myOtherFunction() //working
}

You can also make anonymous callback functions async:

myMethod().then(async () => {
  await myAsyncCall()
})

Answer 4

You don't read that error message right: the problem isn't the function you're calling but the function you're in.

You may do

(async function(){
    await dbc.solve(img);
    // more code here or the await is useless
})();

Note that this trick should soon enough not be needed anymore in node's REPL: https://github.com/nodejs/node/issues/13209