如何将 Async.js eachSeries 示例转换为 Bluebird Promises？

Question

我正在研究 Promises 并想知道是否有人熟悉 Async.js 可以演示如何使用 Bluebird promises 执行以下操作。这是我能想到的最简单直接的示例来演示 Async.js eachSeries。对于不熟悉 Async.js 的任何人，此示例对每个数组元素运行相同的过程，运行串行（一个接一个而不是并行），然后在所有异步操作完成后执行代码.

var async = require('async');

var items = [0,1,2,3,4,5,6,7,8,9]; // this is to simulate an array of items to process

async.eachSeries(items,
    function(item, callback){
        console.log('start processing item:',item);
        //simulate some async process like a db CRUD or http call...
        var randomExecutionTime = Math.random() * 2000;
        setTimeout(function(index){
                        //this code runs when the async process is done
                        console.log('async Operation Finished. item:',index);
                      callback(); //call the next item function
                    },randomExecutionTime,item);
    },
    function(err){
        if(err){
            console.log('Got an error')
        }else{
            console.log('All tasks are done now...');
        }
    }
);

干杯
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Answer 1

我重新格式化并删除了注释，但这与您的 async 代码具有相同的行为。关键是Promise.each，它是串行工作的。请注意 Promise.each 解析为原始数组。也就是说，如果您在传递给最终 then 的函数中采用参数，它将得到 [0,1,2,3,4,5,6,7,8,9].

Promise.delay 本质上是 setTimeout 的简单包装。

var Promise = require('bluebird');

var items = [0,1,2,3,4,5,6,7,8,9];

Promise.each(items, function(item) {
  console.log('start processing item:',item);
  var randomExecutionTime = Math.random() * 2000;
  return Promise.delay(randomExecutionTime)
  .then(function() {
    console.log('async Operation Finished. item:', item);
  });
}).then(function() {
  console.log('All tasks are done now...');
}).catch(function() {
  console.log('Got an error')
});

如何将 Async.js eachSeries 示例转换为 Bluebird Promises？

how to convert Async.js eachSeries example to Bluebird Promises?

javascript

asynchronous

node.js

promise

async.js