节点js等待在catch块抛出错误中进行的异步调用

Question

I'm completely new to javascript and was learning how to use await with async functions. In my case I'm trying to wait for an async function to complete which I've called from a catch block. It isn't working with the message The await operator can only be used with async functions .

begin().then( () =>
    console.log("done")
)

async function begin() {
    await shouldFail().then( message =>
        console.log(message)
    ).catch( () => {
        await shouldFail().then( message => // The await here is not working. 
            console.log(message)
        ).catch( message =>
            console.log(message)
        )
    })
}

async function shouldFail(){
    await sleep(1000)
    return new Promise((resolve, reject) => reject('failed'))
}

I can understand this could be happening because the catch method might not be async. I've tried to simplify my case with the above code. What would be the best way to know when the async function called inside the catch block is completed? I want the begin to only return after the catch block has executed.

Answer 1

According to definition: await can be used only in async functions.

So your nested function has to async be as well

async function begin() {
    await shouldFail().then( message =>
        console.log(message)
    ).catch( async () => { // here -----------------
        await shouldFail().then( message => 
            console.log(message)
        ).catch( message =>
            console.log(message)
        )
    })
}

Answer 2

begin().then( () => console.log("done") ) async function begin() { await shouldFail().then( message => console.log(message) ).catch(async () => { //**Just add a async here** await shouldFail().then( message => // This should work now console.log(message) ).catch( message => console.log(message) ) }) } async function shouldFail(){ await sleep(1000) return new Promise((resolve, reject) => reject('failed')) }

Answer 3

when you use async/await then you don't need to add the then and catch block.

You can read more about async/await on MDN

Sample code with async/await

begin().then(() =>
    console.log("done")
)
async function begin() {
    try {
        let message = await shouldFail();
        console.log(message)
    } catch (e) {
        try {
            let message = await shouldFail();
            console.log(message)
        } catch (error) {
            console.log(message)
        }
    }
}
async function shouldFail() {
    await sleep(1000)
    return new Promise((resolve, reject) => reject('failed'))
}