Node.js - Promise 回调覆盖自定义对象

Question

This is my first post to this site, so I apologize in advance of any lack of data or tags, etc. I've been using this site for years, and it always helped me, but now I'm truly lost, and I couldn't find an answer anywhere.

I have an application where I need to call a web service 10 times, each time with a different parameter. The return payload is complex, so I created a custom object to hold the data. I need data from all 10 calls before moving forward with my code, which led me to callback hell. I'm trying to use Promises to simplify this, but this is where I'm facing this weird issue. I'm able to replicate this issue with a simple class:

Custom Object (Person):

var person = {
  firstName : String,
  lastName : String,
  age : Number
}

function Person() { //getters and setters
} module.exports = Person;

Function getToken (returns a specific token my web service calls need), here replaced with a simple string:

function getToken() {

  return new Promise(function(resolve, reject) {
      var x = "random token";
      console.log('getting token');
      setTimeout(function(){resolve(x)}, 200);
    });
}

Function getAction: in my real app, it calls the web service. Here it just creates a random person with an ID as input:

function getAction(uuid) {
  return new Promise(resolve => {
      var newPerson = new Person();
      newPerson.setFirstName("John " + uuid);
      newPerson.setLastName("Doe");
      newPerson.setAge(20);
      console.log("---> Returning Person " + newPerson.getFirstName());
      setTimeout(function(){resolve(newPerson)}, 300);
  });
}

Function getActions: calls getAction for each input parameter. This function itself must return a Promise because there's another function waiting for all the data to be available before continuing.

function getActions() {

 return new Promise(function(resolve, reject) {

  getToken().then(async function(tokenret) {

      var userIds =   ["001", "002", "003", "004", "005", "006", "007", "008", "009", "010" ];

      var myPromise = Promise.join;
      myPromise(getAction(userIds[0]), getAction(userIds[1]), getAction(userIds[2]), function(personOne, personTwo, personThree) {
        console.log("Person One: " + personOne.getFirstName());
        console.log("Person Two: " + personTwo.getFirstName());
        console.log("Person Three: " + personThree.getFirstName());
      });

  }).catch(function(rej) {console.log("Promise Failed! " + rej);});

  });
}

The output for this execution is:

---> Returning Person John 001
---> Returning Person John 002
---> Returning Person John 003
Person One: John 003
Person Two: John 003
Person Three: John 003

We can see that the getAction function was executed in the right order, with the right parameters. But all 3 variables created in the getActions function have the value from the last execution.

I also tried this code:

      const allPromises = userIds.map(userIds => getAction(userIds));

      await Promise.all(allPromises).then(function(allResults) {

        console.log("Received " + allResults.length + " records");
        var thisPersonZero = allResults[0];
        console.log("This person 0: " + thisPersonZero.getFirstName());
        var thisPersonOne = allResults[1];
        console.log("This person 1 " + + thisPersonOne.getFirstName());
        var thisPersonTwo = allResults[2];
        console.log("This person 2 " + + thisPersonTwo.getFirstName());
        console.log("Recapping");
        console.log("This person 0: " + thisPersonZero.getFirstName());
        console.log("This person 1: " + thisPersonOne.getFirstName());
        console.log("This person 2: " + thisPersonTwo.getFirstName());

      });

And I got this output:

---> Returning Person John 001
---> Returning Person John 002
---> Returning Person John 003
---> Returning Person John 004
---> Returning Person John 005
---> Returning Person John 006
---> Returning Person John 007
---> Returning Person John 008
---> Returning Person John 009
---> Returning Person John 010
Received 10 records
This person 0: John 010
This person 1 John 010
This person 2 John 010
Recapping
This person 0: John 010
This person 1: John 010
This person 2: John 010

Finally, I tried using await, which generated even weirder results:

      var firstPerson = await getAction(userIds[0]);
      console.log("First Person: " + firstPerson.getFirstName());
      var secondPerson = await getAction(userIds[1]);
      console.log("Second Person: " + secondPerson.getFirstName());
      console.log("Recapping");
      console.log("First Person: " + firstPerson.getFirstName());
      console.log("Second Person: " + secondPerson.getFirstName());

Result:

---> Returning Person John 001
First Person: John 001
---> Returning Person John 002
Second Person: John 002
Recapping
First Person: John 002
Second Person: John 002

So the value is correct, until the callback for the next Promise, which replaces the value for all the variables. The behavior is the same if I create copies of the variable, even using JSON.parse(JSON.stringify()).

This code works perfectly if I use strings instead of the Person object. However it would be extremely cumbersome to try and do this without custom objects.

I'm sure that I am making some very basic mistake, but even though this seems to be very straightforward, I couldn't find anything on this particular issue anywhere. This issue is happening with Node versions 9.5 and 10, running on MacOS (if it makes any difference).

Any help will be very much appreciated. Thanks in advance!

Full code snippet:

 // Person.js var person = { firstName : String, lastName : String, age : Number } function Person() { Person.prototype.setFirstName = function(firstName) { person.firstName = firstName; } Person.prototype.setLastName = function(lastName) { person.lastName = lastName; } Person.prototype.setAge = function(age) { person.age = age; } Person.prototype.getFirstName = function() { return (typeof person.firstName === 'undefined') ? '' : person.firstName; } Person.prototype.getLastName = function() { return (typeof person.lastName === 'undefined') ? '' : person.lastName; } Person.prototype.getAge = function() { return (typeof person.age === 'undefined') ? 0 : person.age; } } module.exports = Person; // Error.js var Promise = require('bluebird'); var Person = require("./models/Person"); function getToken() { return new Promise(function(resolve, reject) { var x = "random token"; console.log('getting token'); setTimeout(function(){resolve(x)}, 200); }); } function getActions() { return new Promise(function(resolve, reject) { getToken().then(async function(tokenret) { var userIds = ["001", "002", "003", "004", "005", "006", "007", "008", "009", "010" ]; /* var myPromise = Promise.join; myPromise(getAction(userIds[0]), getAction(userIds[1]), getAction(userIds[2]), function(personOne, personTwo, personThree) { console.log("Person One: " + personOne.getFirstName()); console.log("Person Two: " + personTwo.getFirstName()); console.log("Person Three: " + personThree.getFirstName()); }); */ var firstPerson = await getAction(userIds[0]); console.log("First Person: " + firstPerson.getFirstName()); var secondPerson = await getAction(userIds[1]); console.log("Second Person: " + secondPerson.getFirstName()); console.log("Recapping"); console.log("First Person: " + firstPerson.getFirstName()); console.log("Second Person: " + secondPerson.getFirstName()); /* const allPromises = userIds.map(userIds => getAction(userIds)); await Promise.all(allPromises).then(function(allResults) { for (var x = 0; x < allResults.length; x++) { var thisPerson = allResults[x]; console.log("This Person: " + thisPerson.getFirstName()); } console.log("Received " + allResults.length + " records"); var thisPersonZero = allResults[0]; console.log("This person 0: " + thisPersonZero.getFirstName()); var thisPersonOne = allResults[1]; console.log("This person 1 " + thisPersonOne.getFirstName()); var thisPersonTwo = allResults[2]; console.log("This person 2 " + thisPersonTwo.getFirstName()); console.log("Recapping"); console.log("This person 0: " + thisPersonZero.getFirstName()); console.log("This person 1: " + thisPersonOne.getFirstName()); console.log("This person 2: " + thisPersonTwo.getFirstName()); }); */ }).catch(function(rej) {console.log("Promise Failed! " + rej);}); }); } function getAction(uuid) { return new Promise(resolve => { var newPerson = new Person(); newPerson.setFirstName("John " + uuid); newPerson.setLastName("Doe"); newPerson.setAge(20); console.log("---> Returning Person " + newPerson.getFirstName()); setTimeout(function(){resolve(newPerson)}, 300); }); } getActions();

Answer 1

Without going too much into your code, I can already tell you that your Person 'class' methods are using person object declared at the top of the Person.js file. Fix those to use this and that should be it.

Person.prototype.setFirstName = function(firstName) { this.firstName = firstName; }

The way you have it set now the methods keep mutating the same object.