auto increment in mongoose + nodejs
...
var bookSchema = new Schema({
author: { type: Schema.Types.ObjectId, ref: 'Author' },
title: String,
genre: String,
publishDate: Date
});
bookSchema.plugin(autoIncrement.plugin, 'Book');
var Book = connection.model('Book', bookSchema);
````
That's it. Now you can create book entities at will and they will have an `_id` field added of type `Number` and will automatically
increment with each new document. Even declaring references is easy, just remember to change the reference property's type
to `Number` instead of `ObjectId` if the referenced model is also using the plugin.
````js
var authorSchema = new mongoose.Schema({
...