How to update multiple Mongo documents manually in NodeJs?

Question

I have a collection of users in MongoDB. I need to generate a token for each user and save it to the database:

var crypto = require('crypto');
db.users.find({}).exec(function(users){
    users.forEach(function(user){
       user.token = crypto.randomBytes(32).toString('hex');
       user.save();
    });
});

I'm always confused about async methods and just can't understand how they work... So this code doesn't work beacuse it exists before the save() calls finish. How would you make it work? How would you wait for all the save()˙calls and print Done! to console?

Thanks!

alexmac · Accepted Answer · 2016-05-07 13:40:51Z

2

Mongoose find function returns a promise, you can use it to create chain. Promise.all produces promises (or a mix of promises and values), iterate over all the values and return a promise that is fulfilled when all the items in the array are fulfilled.

var crypto = require('crypto');

db.users
    .find({})
    .then(users => {
      var ops = users.map(user => {
       user.token = crypto.randomBytes(32).toString('hex');
       return user.save();
      });
      return Promise.all(ops);
    })
    .then(() => console.log('done'))
    .catch(err => console.log('error' + err));
});

answered May 7, 2016 at 13:40

alexmac

19.7k7 gold badges64 silver badges74 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

papaiatis Over a year ago

What does "=>" mean ? I'll try your solution soon.

alexmac Over a year ago

=> means ES6 arrow function syntax. If you use node.js version< 4, use usual functions instead.

papaiatis Over a year ago

Thanks a lot! Works flawlessly.

Collectives™ on Stack Overflow

How to update multiple Mongo documents manually in NodeJs?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related