Node.js loop malfunctioning is causing issues

Question

Node.js loop malfunctioning is causing issues

Having some trouble with my Node.js for loop not functioning synchronously. Looking for assistance, thanks in advance!

Below is the code snippet:

 notifyRide:function*(body){
  yield User.find({_id: {$ne: body.userId}}, function(err, doc){
   if(doc != null){
    User.findOne({_id: body.userId}, function(err, user){
     Ride.findOne({_id : body.rideid}, function*(err1, ride){
      for (var i = 0; i < doc.length; i++) {
       console.log(i)// getting 0
       yield rideStatus.findOne({$and:[{receiver_id:doc[i]._id},{ride_id:body.rideid}]}, function(err, response)
       {
         console.log(i);//getting 1
       })
      }
     })
   })
  }
})

}

node.js mongoose koa

Answer 1

Answer №1

When working with generator-based coroutines, it is important to utilize the promises returned by Mongoose methods instead of relying on nested functions. You can find more information about using promises in Mongoose at:

http://mongoosejs.com/docs/promises.html

For instance, rather than:

Ride.findOne({_id : body.rideid}, function*(err1,ride) ...

You should use:

let ride = yield Ride.findOne({_id : body.rideid});

To avoid complications with generators and ensure that your yielded values are not ignored.

Additionally, if you plan to work with generator-based coroutines, be sure to properly wrap your generator functions. For example:

notifyRide:function*(body) {
  // ...
}

You may want to consider using co like this:

notifyRide: co.wrap(function* (body) {
  // ...
})

or Bluebird like this:

notifyRide: P.coroutine(function* (body) {
  // ...
})

Alternatively, you can explore using async and await:

notifyRide: async (body) => {
  // ...
  // Use 'await' instead of 'yield'
}

Remember that coroutines themselves always return promises.

Lastly, don't forget to maintain proper indentation. It is highly recommended to adhere to a style guide such as the one provided by Airbnb:

Answer 2

When working with generator-based coroutines, it is important to utilize the promises returned by Mongoose methods instead of relying on nested functions. You can find more information about using promises in Mongoose at:

http://mongoosejs.com/docs/promises.html

For instance, rather than:

Ride.findOne({_id : body.rideid}, function*(err1,ride) ...

You should use:

let ride = yield Ride.findOne({_id : body.rideid});

To avoid complications with generators and ensure that your yielded values are not ignored.

Additionally, if you plan to work with generator-based coroutines, be sure to properly wrap your generator functions. For example:

notifyRide:function*(body) {
  // ...
}

You may want to consider using co like this:

notifyRide: co.wrap(function* (body) {
  // ...
})

or Bluebird like this:

notifyRide: P.coroutine(function* (body) {
  // ...
})

Alternatively, you can explore using async and await:

notifyRide: async (body) => {
  // ...
  // Use 'await' instead of 'yield'
}

Remember that coroutines themselves always return promises.

Lastly, don't forget to maintain proper indentation. It is highly recommended to adhere to a style guide such as the one provided by Airbnb:

Node.js loop malfunctioning is causing issues

Answer №1

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