javascript - 错误: Uncaught (in promise): Unhandled promise rejections

Question

此连接预计会出错，但我应该能够捕获 promise 拒绝。但我得到的结果是未处理的 promise 拒绝。 (正如预期的那样，我从 console.log() 得到了 double mongoError )感谢您的建议和建议。

mongodbModule.js 文件

var connection;
module.exports.mongodbConnect = () => {
    return new Promise(async (resolve, reject) => {
        if (!connection) {
            try {
                connection = await mongoClient.connect(uri, opts);
                let database = connection.db(dbName);
                resolve(database)
            } catch (mongoErr) {
                console.log(mongoErr);
                reject(mongoErr);
            }
        }
    });
};

app.js

const mongoConnect = require('./modules/mongodbModule').mongodbConnect;
const connectDb = () => {
    return new Promise( async (resolve,reject) => {
        try {
            let db = await mongoConnect()
            resolve(db);
        } catch (err) {
            reject(err);
        }
    });
};

connectDb()
    .then((db) => {
        console.log(db)
    })
    .catch((mongoErr) => {
        console.log(mongoErr)
        throw mongoErr;
    });

错误

(node:26864) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): MongoNetworkError: failed to connect to server [localhost:27017] on first connect [MongoNetworkError: connect ECONNREFUSED 127.0.0.1:27017]
(node:26864) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Answer 1

您不应该将错误抛出到 catch 中。

.catch(e => {
    console.log(e);
    process.exit(1); // to exit with no error use 0
 });

Express.js 中抛出的错误将关闭您的应用程序。