如何在Nodejs中添加额外的验证来映射？

Question

I have my code

  // take data from and check email if it exists 
  const response = await client.getEntries({content_type:'user'});
  let userData = response.items.map(i => i.fields).find(obj =>{
    if(obj.email == user)
      return true;
  })

  // return 401 status if the credential is not match.
  if (user !== userData.email || pwd !== userData.password) {
    return res.status(401).json({
      error: true,
      message: "Email or Password is Wrong."
    });
  }

It works very well until I fill in non-existent email ... then I get "UnhandledPromiseRejectionWarning -> Cannot read property 'email' of undefined" ... as far as I understand in this case "userData" is undefined as well as email.

I tried to add else here

let userData = response.items.map(i => i.fields).find(obj =>{
    if(obj.email == user)
      return true;
    else
      return obj.email = "wrong"; 
  })

But in this case IF checks only first element from map. How to add extra verification? Or how to fix it? Any idea

Answer 1

You have a lot of different approaches here. At the end of the day it is about making sure you don't read the property of the undefined variable.

1. You can filter undefined variables out of the dataset.

response.items.map(i => i.fields).filter(i => !!i).find((obj = {}) =>{...}

2. You can place a default value

let userData = response.items.map(i => i.fields).find((obj = {}) =>{...}

3. You can also place the default check at the if statement level

let userData = response.items.map(i => i.fields).find((obj = {}) =>{ if((obj || {}).email == user) return true; }

4. You can also filter out the "non-existent email" from the API or however, you are getting the data.

Answer 2

You're using the find() method which can potentially returns undefined . Therefore, you have to take into account that userData can be undefined , otherwise, as you've witnessed, the following if condition will fail:

  if (user !== userData.email || pwd !== userData.password) {

  }

You need to add an extra check at the beginning like this one:

  if (!userData || user !== userData.email || pwd !== userData.password) {

  }