Camel Case Keys

Requirements

• Export camelCaseKeys(value) as a named and default function. Accept JSON-compatible values: null, booleans, finite numbers, strings, dense arrays, and plain objects with own enumerable string keys. Traverse nested arrays and objects at any depth.
• Split a key on one or more underscores, hyphens, or whitespace characters, ignoring leading and trailing separators. An all-uppercase ASCII word (letters and digits) is first lowercased. Lowercase the first character of the first word and uppercase the first character of each later word; preserve the remaining mixed-case letters.
• Examples: user_name becomes userName; API_URL becomes apiUrl; first-name becomes firstName; UserName becomes userName; userID stays userID; user_profileURL becomes userProfileURL. Keys containing only separators become the empty string. Unicode case normalization is outside scope.
• Preserve array order and primitive values, recursively transforming objects inside arrays. Return fresh objects and arrays even when their keys need no changes. Do not mutate input objects or arrays.
• Use only own enumerable string keys; ignore inherited and symbol properties. A null-prototype input object is supported. Output objects have the ordinary Object.prototype and own writable enumerable data properties.
• If multiple input keys normalize to the same key, the last one in Object.keys enumeration order wins. Treat keys such as constructor and toString as data; never alter an output prototype.
• In TypeScript define a recursive JsonValue type and return JsonValue. The normalized keys change the object shape, so preserving the exact input object type is not required.
• Circular references, sparse arrays, Date, Map, Set, functions, undefined, property getters with side effects, and extreme call-stack depth are outside scope. Do not use a library to perform the key conversion.

Examples

Input: { "user_name": "Ada", "API_URL": "/users" }
Output: { "userName": "Ada", "apiUrl": "/users" }

Input: { "user_profile": { "first-name": "Ada" }, "all_users": [{ "user_id": 1 }] }
Output: { "userProfile": { "firstName": "Ada" }, "allUsers": [{ "userId": 1 }] }

Input: { "first_name": 1, "first-name": 2 }
Output: { "firstName": 2 }