Javascript 从回调函数内部向express router发送值

当我从帖子中保存新作者时，我希望返回一条消息，说明新作者已被保存。（如果作者已经存在，我最终还想返回一些内容）我遇到的问题是，尽管作者在DB中获得了save，但我无法从author.save（）的回调参数中写入res.locals.messages。（另外，请注意createAuthor是一个调用数组-我不确定这是否会使获取

result

的值变得更加困难。）

如何将

result

的值传递给路由器

路线：

router.post('/', authorController.createAuthor, (req, res) => {
    res.json({ messages: res.locals.messages})
})

控制器：

exports.createAuthor = [

check('firstName', 'First name must be specified').isLength({min: 1}).trim(),
check('lastName', 'Last name must be specified').isLength({min: 1}).trim(),
sanitizeBody('firstName').trim().escape(),
sanitizeBody('lastName').trim().escape(),


(req, res, next) => {

    const errors = validationResult(req);
    var author = new Author({
        firstName: req.query.firstName,
        lastName: req.query.lastName
    });

    if (errors.isEmpty()) {

       //Edit: added find before save function:
        const query = {$or:[{firstName:{$regex: req.query.firstName, $options: 'i'}},
                {lastName:{$regex: req.query.lastName, $options: 'i'}}]} //TODO this regex fails if a parameter is missing.

        Author.findOne(query).sort([['lastName', 'ascending']]).exec((err, author) => {
            if (err) {
                return next(err)
            }

            if(!(author ==null)){
                var result = {status: "Author already exists: ", author_id: String(author.id)}
                res.locals.messages = result;
                next();
            }

        });


        author.save(function (err, newAuthor) {
            if (err) {
                return next(err)
            }

            var result = {status: "New author saved", author_id: String(newAuthor.id)}
            res.locals.messages = result;

        });
    }
    next();

}
];

---

处理保存并设置

res.locals

值后，需要调用

next

：

exports.createAuthor = [

check('firstName', 'First name must be specified').isLength({min: 1}).trim(),
check('lastName', 'Last name must be specified').isLength({min: 1}).trim(),
sanitizeBody('firstName').trim().escape(),
sanitizeBody('lastName').trim().escape(),


(req, res, next) => {

    const errors = validationResult(req);
    var author = new Author({
        firstName: req.query.firstName,
        lastName: req.query.lastName
    });

    if (errors.isEmpty()) {
        author.save(function (err, newAuthor) {
            if (err) {
                return next(err)
            }

            var result = {status: "New author saved", author_id: String(newAuthor.id)}
            res.locals.messages = result;
            next();


        });
    } else {
        // Remember to do something about these non-empty errors!
        next(new Error('Got more than 0 errors'));
    }

}
];

---

另外，不要忘了处理验证错误数量不为零的情况：）

使用Chris Foster的评论，我能够实现这一点：

exports.createAuthor = [

check('firstName', 'First name must be specified').isLength({min: 1}).trim(),
check('lastName', 'Last name must be specified').isLength({min: 1}).trim(),
sanitizeBody('firstName').trim().escape(),
sanitizeBody('lastName').trim().escape(),


(req, res, next) => {

    const errors = validationResult(req);
    var author = new Author({
        firstName: req.query.firstName,
        lastName: req.query.lastName
    });

    if (errors.isEmpty()) {
        //TODO - Fix this query.
        const query = {
            $or: [{firstName: {$regex: req.query.firstName, $options: 'i'}},
                {lastName: {$regex: req.query.lastName, $options: 'i'}}]
        } 

        Author.findOne(query).sort([['lastName', 'ascending']]).exec((err, existingAuthor) => {
            if (err) {
                return next(err)
            }

            if (!(existingAuthor == null)) {
                var result = {status: "Author already exists: ", author_id: String(existingAuthor.id)}

                res.locals.messages = result;
                next();
            } else if (existingAuthor == null) {

                author.save(function (err, newAuthor) {
                    if (err) {
                        return next(err)
                    }

                    var result = {status: "New author saved", author_id: String(newAuthor.id)}
                    res.locals.messages = result;
                    next();
                });

            }
        });
    }
}
];

---

谢谢你，克里斯。我添加了一个函数，在保存之前检查作者是否存在。查找的结果是

作者已存在：

但是，新作者将再次保存。如何确保新作者在确认已存在于数据库中后不会再次保存？我已尝试从“查找”中设置标志。。。请给我一秒钟时间更新我的原始代码。当调用

Author.findOne（query）.sort

时，它将立即转到下一个操作并执行

Author.save

。之后，将调用

Author.findOne（query）.sort的回调，您将检查结果，但此时它已经在尝试保存新的作者了！您需要将
author.save
函数放入
author.findOne（query）.sort
的回调函数中，并仅在结果良好时调用它。基于您最初的问题和后续代码，我认为您试图编写回调函数，但对回调的工作原理没有深入了解。在继续之前，您应该对回调进行一些研究，否则会有很多麻烦！我可以推荐。谢谢你，克里斯。我在这里做的是一种盲目的尝试，但是，我可以通过你的评论来实现这一点。我会再检查一遍。