小编Abh*_*wal的帖子

我正在学习 Promise 库，但遇到了以下问题。

//Function for getting sum
    function getSum(n1, n2) {   
       var isAnyNegative = function() {   
          return n1 < 0 || n2 < 0;   
       }
       var promise = new Promise(function(resolve, reject) {   
          if (isAnyNegative()) {   
             reject(Error("Negatives not supported"));   
          }   
          resolve(n1 + n2)
       });   
       return promise;   
    }

 ////Function for getting Difference
    function getDiff(n1,n2){
        var diff = n1-n2;
        setTimeout(function(){
            console.log("value of diff--- ", diff)
            return diff;
        }, 2000)
    }

    getSum(5,6)
    .then(function(callbackResult){
        console.log("first callback-Result- ", callbackResult)
        return getDiff(14,11);
    }, function(error){
        //handling error
    }) …

当我使用 NodeJS 和 Sequelize 连接访问数据库时，我想更改来自 Mysql 数据库的最终输出中的默认列名。我正在使用以下代码进行连接：-

import Sequelize from "sequelize";

    let dbConnection = new Sequelize('DB', 'abc', 'password', {
        host: '127.0.0.1',
        port: 4242,
        dialect: 'mysql',
        dialectOptions: {
            requestTimeout: 0,
        },
    });

const Listing = dbConnection.define('TableName', {
    tour_title: {
        type: Sequelize.STRING,
    }
}, { freezeTableName: true, timestamps: false });

例如，我只想在最终的续集输出中通过上列中的 tour_name 更改 tour_title。我不希望对数据库列名称进行任何更改。

下面是使用async-waterfall方法的代码段.我怎么能用诺言转换这个.

async.waterfall([
    function(callback){
     User.update({username: user.username}, {$set: update_list}, function(err, a_user) {
      if (err) {
        err = new Error();
        err.code = 400;
        err.message = "Unexpected error occurred."
        callback(err)
      }
      if (!a_user) {
        err = new Error();
        err.code = 400;
        err.message = "User not found."
        callback(err)
      }else{
        callback(null, "updated", user_image);
      }
    })
   }, function(message, user_image, callback){
    if(user_image == undefined){
      callback(null, "done")
    }else{
      Bean.update({username: user.username, status:"Active"}, {$set: {user_image:user_image}},{multi:true},function(err, beanUpdated){
        if(err){
          err = new Error();
          err.code = 400;
          err.message = "Unexpected error occurred."
          callback(err)
        }else{ …