How to organize the list of asynchronous functions?

Question

I am trying to write "robocopy / mir" as a function in Node.js and it seems that I cannot plunge into the head how to correctly execute several asynchronous functions in order.

Some background:

• The script runs on Windows, so I need to find a way to copy files, saving modification time and getting progress notifications.
• To solve this problem, I continued to work and wrote my copy function in .NET (calling it using Edge.js). This copy function simply returns a request to copy the Node message file. This thing works flawlessly.

To copy files in order, my first thought was this:

Object.keys(filesToCopy).forEach(function(key) {
    var deferred = q.defer();
    var payload = {
        sourcePath: key,
        destPath: filesToCopy[key],
        progressCallback: progressCallback
    };

    console.log('Copying %s...', sourcePath);
    // Edge.js called here
    copyFile(payload, deferred.makeNodeResolver());

    deferred.promise.then(function(result) {
        console.log('%s complete.', result);
    }, function(err) {
        console.error('Error: ', err.message);
    });

    promises.push(deferred.promise);
});

, ( ) , .NET, , , :

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: , , , Edge.js . , filesToCopy, - :

  return filesToCopy.reduce(function(prev, curr) {
    return prev.then(function() {
      var deferred = q.defer();
      copyFile(curr, function(err, result) {
        deferred.resolve(result);
        console.log('Completed %s', result);
      });
      return deferred.promise;
    })
  }, q());

, .

Answer 1

, - :

var $j = function(val, space) {
  return JSON.stringify(val, null, space || '')
}
var log = function(val) {
  document.body.insertAdjacentHTML('beforeend', '<div><pre>' + val + '</div></pre>')
}



var files = '12345'.split('').map(function(v) {
  return {
    name: 'file_' + v + '.js',
    load: function() {
      var cur = this;
      var pro = new Promise(function(resolve, reject) {

        log('loading : ' + cur.name);
        
        // we simualate the loading stuff
        setTimeout(function() {
          resolve(cur.name);
        }, 1 * 1000);

      }).then( function( val ) {
        
        // once loaded 
        log('loaded : ' + val);
        return val;
      
      });

      return pro;

    }
  };
});


files.reduce(function(t, v) {

  t.promise = t.promise.then(function(){ 
      return v.load();
  });
  
  return t;
}, {
  promise: Promise.resolve(1)
});

Answer 2

async.eachSeries async.forEachOfSeries .

var async = require('async');
var filesObject = {'file/path/1': {}, 'file/path/2': {}};

async.forEachOfSeries(filesObject, copyFileFromObj, allDone);

function copyFileFromObj(value, key, callback) {
  console.log('Copying file ' + key + '...');
  callback(); // when done
}

function allDone(err) {
  if (err) {
    console.error(err.message);
  }
  console.log('All done.');
}                

var async = require('async');
var filesArray = ['file/path/1', 'file/path/2'];

async.eachSeries(filesArray, copyFile, allDone);

function copyFile(file, callback) {
  console.log('Copying file ' + file + '...');
  callback(); // when done
}

function allDone(err) {
  if (err) {
    console.error(err.message);
  }
    console.log('All done.');
}

: https://tonicdev.com/edinella/sync-loop-of-async-operations