Case Converter

Case conversion involves two phases: tokenization and reconstruction. First, the input text is split into individual words by detecting word boundaries — these include spaces, hyphens, underscores, and camelCase transitions (lowercase-to-uppercase). A regex like `/[A-Z]?[a-z]+|[A-Z]+(?=[A-Z][a-z]|\d|\b)|[A-Z]|\d+/g` captures each word token, including abbreviations and numbers.

Once tokenized, each casing format applies its own reconstruction rules: UPPERCASE calls `toUpperCase()` on every token and joins with the original separator. camelCase lowercases the first token and capitalizes the first letter of subsequent tokens, joining without separators. snake_case lowercases all tokens and joins with underscores. Title Case capitalizes the first letter of each word, with optional handling for articles and prepositions (a, an, the, of, in) to follow English title capitalization rules. Sentence case capitalizes only the first word and proper nouns. The converter preserves non-alphabetic characters (numbers, punctuation) in their original positions.