Node.js返回值未定义

Question

token in the below snippet is always undefined . Can someone help me out figuring what's wrong here?

[err, token] = await to(comparePassHash(body.password, user.password));`

comparePassHash = async (pass, hash) => {
    bcrypt.compare(pass, hash, (err, token) => {
        if (err) TE(err);
        console.log('test');
        return token;
    });
};


to = (promise) => {
    return promise
    .then(data => {
        return [null, data];
    }).catch(err =>
        [pe(err)]
    );
};

Answer 1

It's undefined because that's what comparePassHash resolves.

async keyword won't work as you expect in that case. You're returning token inside .compare function, not inside comparePassHash . You have to wrap bcrypt.compare with a Promise .

const comparePassHash = (pass, hash) => {
    return new Promise((resolve, reject) => {
        bcrypt.compare(pass, hash, (err, token) => {
            if (err) 
                return reject(err);
            console.log('test');
            return resolve(token);
        });
    });
};

---

Take your function:

comparePassHash = async (pass, hash) => {
    bcrypt.compare(pass, hash, (err, token) => {
        if (err) TE(err);
        console.log('test');
        return token;
    });

   // implicit return: undefined
};

Without an await it will execute bcrypt.compare , it will not wait until it finishes, since it's not a promise, and it will exit the function, returning undefined since you're missing a return statement.

Another way is to use Util.promisify

const { promisify } = require('util');
const comparePassHash= promisify(bcrypt.compare);

// This must be inside an async function
[err, token] = await to(comparePassHash(body.password, user.password));