`@stdlib/string`: `startcase` function does not work when the input string is fully uppercase

[KBeDevel]

Description

Encountered an unexpected result when trying to change the case of an enumerator key

The string is obtained using the logic: Enumerator[Enumerator.EnumeratorKey]

Related Issues

No related issues found (yet)

Questions

No.

Demo

https://codesandbox.io/s/agitated-hill-v37msg?file=/src/App.tsx

Reproduction

- Define/import an enumerator with uppercase string keys
- Use the enumerator value to get the enumerator key (`startcase(Enumerator[Enumerator.ENUMERATOR_KEY])`)

Expected Results

Execute `startcase(StatusCodes[StatusCodes.UNAUTHORIZED])` and obtain `'Unauthorized'`

Actual Results

// The enumerator is exported by the `http-status-codes` library

enum StatusCodes { // Enumerator structure for reference
  ACCEPTED = 202,
  BAD_GATEWAY = 502,
  // ...
  UNAUTHORIZED = 401,
  // ...
};

startcase(StatusCodes[StatusCodes.UNAUTHORIZED]); // -> UNAUTHORIZED

startcase(StatusCodes[StatusCodes.UNAUTHORIZED].toString()) // -> UNAUTHORIZED

startcase(`${StatusCodes[StatusCodes.UNAUTHORIZED]}`); // -> UNAUTHORIZED

startcase("UNAUTHORIZED"); // -> UNAUTHORIZED

The workaround is:

startcase(StatusCodes[StatusCodes.UNAUTHORIZED].toLowerCase()); // -> Unauthorized

Version

"@stdlib/string": "^0.0.13"

Environments

Firefox, Chrome, Microsoft Edge

Browser Version

No response

Node.js / npm Version

noed@17.9.0 / yarn@3.2.0 (npm@8.5.5)

Platform

No response

Checklist

• Read and understood the Code of Conduct.
• Searched for existing issues and pull requests.

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[Planeshifter]

Thank you for filing this issue and providing a detailed description!

The current behavior is intentional and matches our other *case functions such as camelcase and pascalcase in that it leaves uppercase character appearing in the middle of a word intact
(e.g., see [1], [2]).

We tried to convey this via the package description, which is:

Capitalize the first letter of each word in a string.

and have a unit test included to that effect.

We suggest you stick to first lowercasing the string before passing it into the startcase function in order to achieve the desired behavior.