Mongoose JS promises? Or how to manage batch save

Yes, you can do this with promises. If you were using the Q promise library, you could re-write @matz3's code like:

var tasks = [];for (var i=0; i < docs.length; i++) {  tasks.push(docs[i].save());}Q.all(tasks)  .then(function(results) {    console.log(results);  }, function (err) {    console.log(err);  });

We start all the operations one at a time in the loop, but we don't wait for any of them to complete, so they run in parallel. We add a promise (that acts like a placeholder for the result) to an array. We then wait for all the promises in the array of promises to complete.

Most good Promises/A+ compatible libraries have some equivalent to Q.all

mongoose now allows you to choose which Promise implementation.

Here I am using the node.js default system Promise (ES6) baked into nodejs

var mongoose = require('mongoose');    mongoose.Promise = global.Promise; // use system implementationPromise.all(obj1.save(), obj2.save(), obj3.save()).then(function(resultSaves) {    console.log('parallel promise save result :');    console.log(resultSaves);    mongoose.disconnect();}).catch(function(err) {    console.log('ERROR on promise save :');    console.log(err);    mongoose.disconnect();});

node --versionv4.1.1

mongoose@4.1.8

Since mongoose now supports promises you may use Promise.all().then(), so it will return when all promises are resolved.

Promise.all([  obj1.save(),  obj2.save(),  obj3.save()]).then(console.log).catch(console.error)

In fact, if you're always calling the save() method you can use the Array.map() here:

Promise.all([ obj1, obj2, obj3 ].map( obj => obj.save() )

Aaand also use es6 syntax to destructure the resulting array:

Promise.all(  [ obj1, obj2, obj3 ]  .map( obj => obj.save() )).then( ([ savedObj1, savedObj2, savedObj3 ]) => {   // do something with your saved objects...})