如何使用await调用异步箭头函数

Question

If I define a function like this:

const getName = async () => await Promise.resolve('John');

When I try to call the getName function with async:

const name = await getName();
console.log(`Hi ${name}`);

It throws an error:

const name = await getName();
             ^^^^^

SyntaxError: await is only valid in async function

What I'm doing wrong?

Answer 1

 const getName = async () => await Promise.resolve('John'); 

In the above, you have an async function (the arrow function) which uses await inside.

This is fine (albeit pointless as you could return the promise directly).

Here:

 const name = await getName(); 

You use await again, and while the function on the right-hand side does return a promise, the function it appears inside is not async so it is not valid.

---

Put it inside an async function and it will be fine:

 const getName = async() => await Promise.resolve('John'); const init = async() => { const name = await getName(); console.log(`Hi ${name}`); }; init(); 

As mentioned though, making getName async and await ing inside is just a needlessly complex set of nested promises and you could simplify:

 const getName = () => Promise.resolve('John'); const init = async() => { const name = await getName(); console.log(`Hi ${name}`); }; init();