Stop mongoose from creating _id property for sub-document array items

This is very simple, You can do this:

var mongoose = require("mongoose");
var subSchema = mongoose.Schema({
    //your subschema content
},{ _id : false });
var schema = mongoose.Schema({
    // schema content
subSchemaCollection : [subSchema]
});
var model = mongoose.model('tablename', schema);

We can make sub-document without schema and avoid_id. then add _id:false to your subdocument declaration.

var schema = new mongoose.Schema({
   field1:{type:String},
   subdocArray:[{
        _id:false,
        field :{type:String}
   }]
});

It will create an _id field in your subdoc. tested in Mongoose 3.8.1

further, if we using an object literal structure for specifying a sub-schema, you may also just add _id: false to supress it.

{
   sub: {
      property1: String,
      property2: String,
      _id: false
   }
}