JavaScript bracket notation on object returning undefined on existing key

Question

Summary: Unable to access object key value using bracket notation as the existing key is returned as undefined.

I have an array of users (constructed by parsing a CSV files and its columns):

let users = [
  {
    'User ID': '5ef62675b78d747c79086175',
    'Survey Completed Date': '11/12/19',
    'Survey Type': 'Assessment'
  },
  {
    'User ID': '5ef62675b78d827c79086186',
    'Survey Completed Date': '27/12/19',
    'Survey Type': 'Assessment'
  },
  ...
];

For every user, I need to access their User ID in order to make a mongoose query.

  console.log(users) // Logs the above object

  for (let i = 0; i < users.length; i++) {

    const row = users[i];

    // Example with i = 0
    console.log(row) // {
                     //   'User ID': '5ef62675b78d747c79086175',
                     //   'Survey Completed Date': '11/12/19'',
                     //   'Survey Type': 'Assessment'
                     // }
    console.log('User ID' in row)                         // false (??) <<<<<<<<<
    console.log(row['User ID'])                           // undefined (!?!)  <<<<<<<<<
    console.log(row['Survey Completed Date'])             // 11/12/19 (This works however)
    console.log(Object.keys(row)[0])                      // User ID 
    console.log(Object.keys(row)[0].trim() === 'User ID') // true 
    console.log(row[Object.keys(row)[0]])                 // 5ef62675b78d747c79086175 (want to 
                                                          //  avoid using this workaround since 
                                                          //  the properties will not always be 
                                                          //  in the same order)
    
    let userId = row['User ID']                           // (Still undefined)
    let user = await User.findById(userId);

I'm rather stuck. Any help or redirection would be greatly appreciated!

console.log(Object.keys(row)[0].trim() === 'User ID') <-- why do you have .trim() there? Leading or trailing whitespace would explain the problem. — Guy Incognito
– Guy Incognito, Commented Dec 1, 2020 at 17:38
...and in fact there is an invisible whitespace character at the start of the key. — Guy Incognito
– Guy Incognito, Commented Dec 1, 2020 at 17:39
Special character that looks empty on browser - #ef bb bf (utf-8 character) — LogiStack
– LogiStack, Commented Dec 1, 2020 at 17:43

Nikita Ivanov · Accepted Answer · 2020-12-01 17:49:46Z

2

You have an extra invisible whitespace character in keys of all of your objects (at least in those 2 you wrote). I started to copy-pasteing your 'User ID' strings in console, and found out that in your data both User ID keys have this problem.

These invisible characters are rendered as red dots when pasted into my browser's console. I also checked 2 other keys in your data, and they seem to be clear; however, better do a .trim() on object keys when you form your data from a csv file.

FYI, the character that breaks your code is \ufeff, "Zero-width no-break space".

answered Dec 1, 2020 at 17:49

Nikita Ivanov

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Levan Gulisashvili · Accepted Answer · 2020-12-01 17:42:20Z

1

when i copied your code before "User ID" there was one char with question mark and when removed it then row["User ID"] worked just fine. so please try it !

in this codesandbox as you can see here it works just fine

answered Dec 1, 2020 at 17:42

Levan Gulisashvili

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michael · Accepted Answer · 2020-12-01 17:42:43Z

1

There's special character in front of U in 'User Id'. Please try to run this answer. You will see it works.

let users = [
  {
    'User ID': '5ef62675b78d747c79086175',
    'Survey Completed Date': '11/12/19',
    'Survey Type': 'Assessment'
  },
  {
    'User ID': '5ef62675b78d827c79086186',
    'Survey Completed Date': '27/12/19',
    'Survey Type': 'Assessment'
  }
];

for (let i = 0; i < users.length; i++) {
  const row = users[i];
  let userId = row['User ID'];
  console.log(userId);
}

answered Dec 1, 2020 at 17:42

michael

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