我如何检查是否存在电子邮件地址？

我正在学习来自Laravel的NodeJS。我已经在Feathers生成器提供的钩子中设置了用户注册的基本验证。

如何使用用户服务检查数据库中是否已存在电子邮件地址？我正在使用MongoDB作为服务的数据库

const {authenticate} = require('@feathersjs/authentication').hooks;
const validator = require('validator');

const {
    hashPassword, protect
} = require('@feathersjs/authentication-local').hooks;

module.exports = {
    before: {
        all: [],
        find: [authenticate('jwt')],
        get: [authenticate('jwt')],
        create: [hashPassword(),
        function(context) {
            let input = context.data;
            const userService = app.service('users');

            if (validator.isEmpty(input.name)) {
                throw new Error('Please enter your name.');
            }
            if (validator.isEmpty(input.email)) {
                throw new Error('Please enter your email address.');
            } else if (!validator.isEmail(input.email)) {
                throw new Error('Please enter a valid email address.');
            }
            if (validator.isEmpty(input.password)) {
                throw new Error('Please enter a password for your account.');
            }

            userService.find({
                query: {
                    email: input.email
                }
            }).then((users) => {
                console.log(users);
            })
        }
        ],
        update: [hashPassword(), authenticate('jwt')],
        patch: [hashPassword(), authenticate('jwt')],
        remove: [authenticate('jwt')]
    },

    after: {
        all: [
            // Make sure the password field is never sent to the client
            // Always must be the last hook
            protect('password')
        ],
        find: [],
        get: [],
        create: [],
        update: [],
        patch: [],
        remove: []
    },

    error: {
        all: [],
        find: [],
        get: [],
        create: [

        ],
        update: [],
        patch: [],
        remove: []
    }
};

上下文对象允许访问钩子的服务。 （这是问题的解决方案）因此，以下代码可用于确定数据库中是否存在用户的电子邮件地址。

此外，重复的电子邮件检查将在用户插入数据库后执行，因为它是一个承诺。因此，async和await用于在继续之前等待promise的解析。

module.exports = {
    before: {
        all: [],
        find: [authenticate('jwt')],
        get: [authenticate('jwt')],
        create: [hashPassword(),
        async context => {
            let input = context.data;
            //const userService = app.service('users');

            if (validator.isEmpty(input.name)) {
                throw new Error('Please enter your name.');
            }
            if (validator.isEmpty(input.email)) {
                throw new Error('Please enter your email address.');
            } else if (!validator.isEmail(input.email)) {
                throw new Error('Please enter a valid email address.');
            }
            if (validator.isEmpty(input.password)) {
                throw new Error('Please enter a password for your account.');
            }

            await context.service.find({
                query: {
                    email: input.email
                }
            }).then((data) => {
                 if (data.data.length) {
                throw new Error('This email address is already in use by somebody else.');
            }
            });

        }
        ],
        update: [hashPassword(), authenticate('jwt')],
        patch: [hashPassword(), authenticate('jwt')],
        remove: [authenticate('jwt')]
    },