Understanding text case
The same letters, told nine different ways.
Casing is conventional, not technical — but the conventions carry meaning to anyone reading the code or copy.
UPPER, lower, and the in-betweens.
The simplest cases are uniform: every letter UPPER, every letter lower. Sentence case capitalises only the first letter of each sentence; Title Case capitalises most words but conventionally not articles and prepositions; Inverse Case flips whatever you started with. None of these change the underlying characters in any technical sense — they all describe a presentation.
Programmer cases — naming things.
Code identifiers can't contain spaces, so the language picks a packing convention. camelCase for JavaScript variables and Java methods. PascalCase for types, classes, components. snake_case for Python functions and database columns. kebab-case for URL slugs, CSS classes, and Lisp-family languages. CONSTANT_CASE for compile-time constants. They all mean the same thing — multiple words glued together — and the choice is purely a community convention.
Title Case isn't standardised.
Different style guides disagree on which short words to lowercase. AP keeps prepositions of three or fewer letters lowercase; Chicago lowercases all prepositions regardless of length; APA only lowercases words shorter than four letters. The converter uses a pragmatic rule — capitalise everything except a-an-the-and-or-but-of-in-on-at-to-for — which matches what most readers expect.
Unicode and the Turkish I.
Lowercasing is locale-sensitive in a few languages. In Turkish, the lowercase of I is ı (dotless i), not i. JavaScript's plain toLowerCase() doesn't know your locale; the converter uses the same engine, which is fine for English but technically wrong for Turkish text. For locale-correct casing you need toLocaleLowerCase('tr-TR') in code.