从每个回调调用中获取异步nodejs值[重复]

Posted 2023-03-07

【中文标题】从每个回调调用中获取异步nodejs值[重复]

【英文标题】：getting async nodejs value from each callback calls [duplicate]

【发布时间】：2017-04-28 17:22:49

【问题描述】：

var async = require('async');

var square = function (id, callback) 
  Business.prototype.getBusinessUser(id,function(userObject)
    return callback(userObject);
  );
 ;


async.eachSeries(findBusinessResult, function (businessObject, callback) 
//console.log("results from square");
  var result =  square(businessObject["id"] , function(result)
    console.log(result);
  );
  callback(); // Alternatively: callback(new Error());
 , function (err,results) 
   if (err)  throw err; 
   console.log('Well done :-)!');
   console.log(results);
);

为什么结果总是undefined：请帮忙。

【问题讨论】：

看看***.com/q/14220321/5692251

【参考方案1】：

async 是 ES7 中的保留字，以后实现时可能会给您带来问题。 您可能要考虑的实际上是将 async/await 与 babel 一起使用。 一些浏览器已经开始实现它了

var square = id => 
    new Promise(rs => 
        Business.prototype.getBusinessUser(id, rs)
    )

async search() 
    for (let businessObject of findBusinessResult) 
        let result = await square(businessObject.id)
        console.log(result)
    

【参考方案2】：

我希望这对大多数人来说是一个改变游戏规则的解决方案。这使得 ASYC java 回调变成了看起来与高效回调处理同步的东西。这是我三天的挑战。 Callbacks 确实是 javacript 中的一个主要挑战，这里是如何使用 Promise 解决问题。

install bluebird 
npm install bluebird --save

//在你的代码中

var Promise = require('bluebird'); //yeah awsome bird indeed :)

function extendBusinessObjectPromise(id,element) 
    return new Promise(function(resolve, reject) 
        Business.prototype.getBusinessUser( id ,function(userObject)
         var extend = require('util')._extend;
         mergedJson = userObject;
         elements = element;
         extend(,elements);
         extend(elements,mergedJson);
         global.businesssWithUsers.push(elements); //sahred object
        resolve(global.businesssWithUsers)
        )
)

//NOW 我如何在 foreach 循环中调用 promise 结果并将其值作为回调结果返回。似乎很疯狂的想法:(

Person.prototype.getPersons = function(filter , callback) 
  //this my own Bill count since i have one using one user account
  global.businesssWithUsers = [];

models.PersonModel.findAll(filter_combined).then(function (findBusinessResult) 
  global.businesssWithUsers = []
  var extend = require('util')._extend;
  var mergedJsonArray =  [];

  if (findBusinessResult==null) 
    return callback(false,"no result found");
   

   var promiseBusinessResult = null; //promise reslover :)

   var findBusinessResult =JSON.parse(JSON.stringify(findBusinessResult));

    findBusinessResult.forEach(function(eachElement) 
      var id = element["userId"];
      promiseBusinessResult = extendBusinessObjectPromise(id,element);
    );

    promiseBusinessResult.done(function(result)
       callback(true,result); //pass the result to main function
     );

    ).catch(function (err) 
      log.error(err["errors"][0]["message"])
      callback(false,err["errors"][0]["message"])
      return
    )

终于成功了。干杯! Daniel Adenew