setDuplicateEmailValidation(){
    this.schema.path('email').validate((email, fn) => {
        let User = mongoose.model('User');

        // Check only when it is a new user or when email field is modified
        if (this.isNew || this.isModified('email')) {
            User.find({ email: email }).exec((err, users) => {
                fn(!err && users.length === 0);
            });
        } else fn(true);
    }, 'Email already exists');
}

function setDuplicateEmailValidation() {
            var _this = this;
        this.schema.path('email').validate(function (email, fn) {
            var User = _mongoose2['default'].model('User');

            // Check only when it is a new user or when email field is modified
            if (_this.isNew || _this.isModified('email')) {
                User.find({ email: email }).exec(function (err, users) {
                    fn(!err && users.length === 0);
                });
            } else fn(true);
        }, 'Email already exists');
    }
}