每当我将某些内容保存到数据库时，我都会不断收到这个错误。不管它的数字，文本等等，它都会发生，我不知道为什么。两个月前，一切都很好，每次我保存东西时都没有错误，但从一个月前开始，出现了这种情况：
Unhandled rejection TypeError: Cannot read property 'indexOf' of undefined
at model.isSelected (/var/www/html/node_modules/mongoose/lib/document.js:2056:12)
at model.<anonymous> (/var/www/html/node_modules/mongoose-url-slugs/index.js:215:18)
at callMiddlewareFunction (/var/www/html/node_modules/kareem/index.js:483:23)
at next (/var/www/html/node_modules/kareem/index.js:58:7)
at Kareem.execPre (/var/www/html/node_modules/kareem/index.js:87:8)
at Kareem.wrap (/var/www/html/node_modules/kareem/index.js:266:8)
at model.$__validate (/var/www/html/node_modules/kareem/index.js:376:11)
at /var/www/html/node_modules/mongoose/lib/document.js:2226:10
at promiseOrCallback (/var/www/html/node_modules/mongoose/lib/helpers/promiseOrCallback.js:9:12)
at model.Document.validate (/var/www/html/node_modules/mongoose/lib/document.js:2221:10)
at model.validateBeforeSave (/var/www/html/node_modules/mongoose/lib/plugins/validateBeforeSave.js:35:12)
at callMiddlewareFunction (/var/www/html/node_modules/kareem/index.js:483:23)
at next (/var/www/html/node_modules/kareem/index.js:58:7)
at Kareem.execPre (/var/www/html/node_modules/kareem/index.js:87:8)
at Kareem.wrap (/var/www/html/node_modules/kareem/index.js:266:8)
at model.$__save (/var/www/html/node_modules/kareem/index.js:376:11)
at /var/www/html/node_modules/mongoose/lib/model.js:492:10
at /var/www/html/node_modules/mongoose/lib/helpers/promiseOrCallback.js:31:5
at Promise._execute (/var/www/html/node_modules/bluebird/js/release/debuggability.js:384:9)
at Promise._resolveFromExecutor (/var/www/html/node_modules/bluebird/js/release/promise.js:518:18)
at new Promise (/var/www/html/node_modules/bluebird/js/release/promise.js:103:10)
at promiseOrCallback (/var/www/html/node_modules/mongoose/lib/helpers/promiseOrCallback.js:30:10)
我将Node与Mongodb Atlas一起使用，并使用passport进行设置。有人能告诉我是什么原因造成的吗？我忘了提没有"；indexOf"；在代码中，只位于nodemodules文件夹中，这也是为什么这很奇怪的另一个原因。运行Mongoose 5.11.8、Mongoose url slugs 1.0.2和Bluebird 3.7.2。
有一个未处理的next对象调用。
检查您的中间件或mongo钩子是否缺少在中间件/钩子执行之后应该调用的下一个参数(它可能是保存之前对架构对象的预钩子调用(。
几年前我也犯过同样的错误。添加next作为回调函数的参数可能会修复
这里有一个例子作为参考，其中缺少异步函数的next参数将引发类似的错误：
// user.model.js
userScheme.pre('save', async function (next) {
const user = this;
try {
if (!user.isModified('password')) {
return next();
}
// generates the salt to encrypt the password
const salt = await bcrypt.genSalt(10);
// generate hashed password
const hash = await bcrypt.hash(user.password, salt);
// this is the hashed password that we are going to save in the DB
user.password = hash;
} catch (err) {
next(err);
}
});