Generate User NameFix getUserName so that it returns the user’s name as "LastName, FirstName" (without the quotes).Capitalise the first letter of the first and last namesIf the lastname is null, just return firstname without a commae.g. "John" "Smith" should return "Smith, John"

Here is a step-by-step guide on how to fix the getUserName function in JavaScript:

1. First, we need to check if the lastName is null. We can do this using an if statement.

if (lastName === null) {
    return firstName;
}

2. If the lastName is not null, we need to return the user's name as "LastName, FirstName". We can do this using string concatenation or template literals. Also, we need to capitalize the first letter of the first and last names. We can do this using the charAt method and the toUpperCase method.

return lastName.charAt(0).toUpperCase() + lastName.slice(1) + ', ' + firstName.charAt(0).toUpperCase() + firstName.slice(1);

3. Putting it all together, the getUserName function should look like this:

function getUserName(firstName, lastName) {
    if (lastName === null) {
        return firstName.charAt(0).toUpperCase() + firstName.slice(1);
    }
    return lastName.charAt(0).toUpperCase() + lastName.slice(1) + ', ' + firstName.charAt(0).toUpperCase() + firstName.slice(1);
}

This function will return the user's name as "LastName, FirstName" with the first letter of the first and last names capitalized. If the lastName is null, it will just return the firstName without a comma.