I have created many error handlers in order to handle MongoDB errors, one of them is this which is for duplicated data :

我已经创建了许多错误处理程序来处理MongoDB错误，其中一个是用于处理重复数据的：

const dbDuplicateKeyHandler = (error) => {
  console.log(error);   
  
  console.log(error.keyPattern.name);
  
  // const message = `Duplicated field value: (${error.keyValue.name}) Please use another value .`;
  
  return new AppError(400, `Duplicated field value: (${error.keyValue.name}) Please use another value .`); 

the problem is, when I try to insert a duplicated username the error message is printed as I want it to be, but in case I'm trying with a new user name but duplicated email the error.keyValue.name will be undefined. The handler was working correctly in Postman when I was building the API. also I've searched for the Doc that explain mongoDB errors but couldn't find any.
I console logging the error in both cases

问题是，当我尝试插入一个重复的用户名错误消息是打印出来，因为我想它是，但在情况下，我尝试与一个新的用户名，但重复的电子邮件的error.keyValue.name将是未定义的.当我构建API时，处理程序在Postman中正常工作。我也搜索了解释mongoDB错误的文档，但找不到。我控制台记录这两种情况下的错误

console.log("THE ERROR IS ==>",error);   
console.log("error.keyPattern.name IS ==> ",error.keyPattern.name);
console.log("error.keyValue.name IS ==> ",error.keyValue.name);

For duplicated username:

对于重复的用户名：

for duplicated email :

对于重复的电子邮件：

In the case of email you are using:

如果您使用的是电子邮件：

error.keyPattern.name
error.keyValue.name

But it should be:

但它应该是：

error.keyPattern.email
error.keyValue.email 

You are getting undefined because there is no property of keyPattern or keyValue with a name name.

由于没有带名称的keyPattern或KeyValue的属性，因此未定义该属性。

For consistency instead of error.keyValue.name or error.keyValue.email you could just do:

为了保持一致性，而不是error.keyValue.name或error.keyValue.mail，您只需执行以下操作：

console.log("error.keyPattern IS ==> ", Object.entries(error.keyPattern)[0]);
console.log("error.keyValue IS ==> ", Object.entries(error.keyValue)[0]);

//Prints
error.keyPattern IS ==> ["name", 1]
error.keyValue IS ==> ["name", "username"]

error.keyPattern IS ==> ["email", 1]
error.keyValue IS ==> ["email", "[email protected]"]