save() not working with statics in mongoose - node.js

Question

Below are various methods i tried to save documents but did not work. what am i doing wrong? Is it the correct way to use static? Is method needed here? If yes how will it be implemented in this situation?
Method 1:
userSchema.statics.saveUser = function(data, callback){
data.save(callback);
};
Result - save is not a function
Method 2:
userSchema.statics.saveUser = function(data, callback){
data = new userSchema(data);
data.save(callback);
};
Result - userSchema is not a function
Method 3:
userSchema.statics.saveUser = function(data, callback){
var user = new user(data);
data.save(callback);
};
var user = Mongoose.model('user', userSchema);
Result - user is not a function
Edit
Even the below methods does not seem to be working
Method 4:
userSchema.statics.saveUser = function(data, callback){
var user = new this(data);
user.save(callback);
};
Method 5: JohnnyHK suggested way
userSchema.statics.saveUser = function(data, callback){
var user = new this();
user.data = data;
user.save(callback);
};
userSchema is like this
var db = require('../database');
var Mongoose = db.Mongoose;
require('mongoose-long')(Mongoose);
var SchemaTypes = Mongoose.Schema.Types;
var userSchema = new Mongoose.Schema({
_id:{ type: String, required: true, unique:true },
// many fields with type as string and number
.
.
.
Number:{ type: SchemaTypes.Long, min: 0, default: 0},
});
// query functions here
var user = Mongoose.model('user', userSchema);
// exporting model here
Everything works fine if use this.create(data, callback); instead of save but i want to use save for some reasons.
Data before using it for save
[ { _id: '2A864493-52614B19',
name: 'xyz',
date: 'some date',
...
...
...
city: 'adf'
} ]

Answer 1

You need to create an instance of your model, because the save method is only available for instance.
var User = mongoose.model('user', UserSchema);
UserSchema.statics.saveUser = function(data, callback){
var user = new this(data);
user.save(callback);
};
And please, avoid duplication of variables with adding some uppercase. It's more readable and less hazardous.
Mongoose documentation : http://mongoosejs.com/docs/models.html