javascriptintermediate10 minutes

Fix the Bug in Filtering Unique Usernames from an Array

The provided JavaScript function is supposed to return an array of unique usernames from a list of user objects. However, it currently returns duplicates. Your task is to debug and fix the code to ensure it returns only unique usernames.

Challenge prompt

You are given a function getUniqueUsernames that accepts an array of user objects, each having a 'username' property. The function is meant to return an array of unique usernames. However, the current implementation has a bug and returns duplicate usernames. Identify and fix the bug so that the function correctly returns an array with no duplicates.

Guidance

• Examine how the existing code checks for duplicates and why it might be failing.
• Consider using JavaScript data structures or methods better suited for uniqueness checks.
• Test your function on inputs that have repeated usernames to ensure duplicates are removed.

Hints

• Check how the indexOf method is used and if it properly detects duplicates.
• Think about using a Set or an object to track seen usernames more effectively.

Starter code

function getUniqueUsernames(users) {
  const unique = [];
  users.forEach(function(user) {
    if (unique.indexOf(user.username) !== -1) {
      unique.push(user.username);
    }
  });
  return unique;
}

Expected output

getUniqueUsernames([{username: 'alice'}, {username: 'bob'}, {username: 'alice'}, {username: 'carol'}]) // ['alice', 'bob', 'carol']

Core concepts

arraysloopsconditionalsdata structuresarray methods

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