auto-increment using loopback.js and MongoDB

Question

i want to increase mongodb document number automatically using loopback.

I made function in mongo

 function getNextSequence(name) {
   var ret = db.         


        

Answer 1

I would love to add 1 more point to Robins Answer,you can add upsert:true so that it automatically creates the document if it doesn't exist

tweet.observe('before save', function (ctx, next) {

    var app = ctx.Model.app;

    //Apply this hooks for save operation only..
    if(ctx.isNewInstance){
        //suppose my datasource name is mongodb
        var mongoDb = app.dataSources.mongodb;
        var mongoConnector = app.dataSources.mongodb.connector;
        mongoConnector.collection("counters").findAndModify({collection: 'tweet'}, [['_id','asc']], {$inc: { value: 1 }}, {new: true,upsert:true}, function(err, sequence) {
            if(err) {
                throw err;
            } else {
                // Do what I need to do with new incremented value sequence.value
                //Save the tweet id with autoincrement..
                ctx.instance.id = sequence.value.value;

                next();

            } //else
        });
    } //ctx.isNewInstance
    else{
        next(); 
    }
}); //Observe before save..