如何使用async / await获取第二个`then`回调参数？

Question

For example

randomLibPromise.then((data, err) => { // do something with err })

how would I translate that with await? This promise comes from a library so I don't have control over the fact that the error goes through then instead of catch . What I have is:

let data = await randomLibPromise.catch(err)

but I don't get that second parameter and I can't retrieve the error.

Every example I find on Google talk about catch for error handling but not then .

Answer 1

To "fix" the weird promise, you could just throw err if there is one, and return the data otherwise:

var fixed = randomLibPromise.then((data, err) => { 
    if(err) throw err;
    return data;
})

The result will be a promise which does the correct thing, ie passes the data to a then , an error to a catch or, if awaiting, either returns data or throws the error.

fixed.then(data => { /* handle data */ }).catch(err => { /* handle err */ });
// or
try {
    var data = await fixed;
    // handle data
} catch(err) {
    //handle err
}