user.js

sequelize.define('User', {
  id: DataTypes.INTEGER,
	email: {
		type: DataTypes.STRING,
		validate: {
			isEmail: {
				msg: 'Invalid email address.'
			}
		}
	}
}, {
	classMethods: {
		// User.add({ email: 'test@email.com' }, callback(user, error));
		add: function(attributes, callback) {
			var self = this;
			var user = this.build(attributes);
			var errors = user.validate();
			if(errors) {
				callback(null, errors[Object.keys(errors)[0]]);
			}else{
				this.find({
					where: { email: user.email }
				}).success(function(account) {
					if(account) {
						callback(null, 'Email already registered.');
					}else{
						user.save().success(function(user) {
							self.getById(user.id, function(user) {
								callback(user);
							});
						});
					}
				});
			}
		},
		// User.getById(1, callback(user));
		getById: function(id, callback) {
			this.find({ 
				where: { id: id }
			}).success(function(user) {
				callback(user);
			});
		}
	}
});