title-case/dist/index.js

Transform a string into title case following English rules

const TOKENS = /(\S+)|(.)/g;
const IS_SPECIAL_CASE = /[\.#]\p{Alphabetic}/u; // #tag, example.com, etc.
const IS_MANUAL_CASE = /\p{Ll}(?=[\p{Lu}])/u; // iPhone, iOS, etc.
const ALPHANUMERIC_PATTERN = /\p{Alphabetic}+/gu;
const IS_ACRONYM = /^(\P{Alphabetic})*(?:\p{Alphabetic}\.){2,}(\P{Alphabetic})*$/u;
export const WORD_SEPARATORS = new Set(["—", "–", "-", "―", "/"]);
export const SENTENCE_TERMINATORS = new Set([".", "!", "?"]);
export const TITLE_TERMINATORS = new Set([
    ...SENTENCE_TERMINATORS,
    ":",
    '"',
    "'",
    "”",
]);
export const SMALL_WORDS = new Set([
    "a",
    "an",
    "and",
    "as",
    "at",
    "because",
    "but",
    "by",
    "en",
    "for",
    "if",
    "in",
    "neither",
    "nor",
    "of",
    "on",
    "only",
    "or",
    "over",
    "per",
    "so",
    "some",
    "than",
    "that",
    "the",
    "to",
    "up",
    "upon",
    "v",
    "versus",
    "via",
    "vs",
    "when",
    "with",
    "without",
    "yet",
]);
export function titleCase(input, options = {}) {
    const { locale = undefined, sentenceCase = false, sentenceTerminators = SENTENCE_TERMINATORS, titleTerminators = TITLE_TERMINATORS, smallWords = SMALL_WORDS, wordSeparators = WORD_SEPARATORS, } = typeof options === "string" || Array.isArray(options)
        ? { locale: options }
        : options;
    const terminators = sentenceCase ? sentenceTerminators : titleTerminators;
    let result = "";
    let isNewSentence = true;
    // tslint:disable-next-line
    for (const m of input.matchAll(TOKENS)) {
        const { 1: token, 2: whiteSpace, index = 0 } = m;
        if (whiteSpace) {
            result += whiteSpace;
            continue;
        }
        // Ignore URLs, email addresses, acronyms, etc.
        if (IS_SPECIAL_CASE.test(token)) {
            const acronym = token.match(IS_ACRONYM);
            // The period at the end of an acronym is not a new sentence,
            // but we should uppercase first for i.e., e.g., etc.
            if (acronym) {
                const [_, prefix = "", suffix = ""] = acronym;
                result +=
                    sentenceCase && !isNewSentence
                        ? token
                        : upperAt(token, prefix.length, locale);
                isNewSentence = terminators.has(suffix.charAt(0));
                continue;
            }
            result += token;
            isNewSentence = terminators.has(token.charAt(token.length - 1));
        }
        else {
            const matches = Array.from(token.matchAll(ALPHANUMERIC_PATTERN));
            let value = token;
            let isSentenceEnd = false;
            for (let i = 0; i < matches.length; i++) {
                const { 0: word, index: wordIndex = 0 } = matches[i];
                const nextChar = token.charAt(wordIndex + word.length);
                isSentenceEnd = terminators.has(nextChar);
                // Always the capitalize first word and reset "new sentence".
                if (isNewSentence) {
                    isNewSentence = false;
                }
                // Skip capitalizing all words if sentence case is enabled.
                else if (sentenceCase || IS_MANUAL_CASE.test(word)) {
                    continue;
                }
                // Handle simple words.
                else if (matches.length === 1) {
                    // Avoid capitalizing small words, except at the end of a sentence.
                    if (smallWords.has(word)) {
                        const isFinalToken = index + token.length === input.length;
                        if (!isFinalToken && !isSentenceEnd) {
                            continue;
                        }
                    }
                }
                // Multi-word tokens need to be parsed differently.
                else if (i > 0) {
                    // Avoid capitalizing words without a valid word separator,
                    // e.g. "apple's" or "test(ing)".
                    if (!wordSeparators.has(token.charAt(wordIndex - 1))) {
                        continue;
                    }
                    // Ignore small words in the middle of hyphenated words.
                    if (smallWords.has(word) && wordSeparators.has(nextChar)) {
                        continue;
                    }
                }
                value = upperAt(value, wordIndex, locale);
            }
            result += value;
            isNewSentence =
                isSentenceEnd || terminators.has(token.charAt(token.length - 1));
        }
    }
    return result;
}
function upperAt(input, index, locale) {
    return (input.slice(0, index) +
        input.charAt(index).toLocaleUpperCase(locale) +
        input.slice(index + 1));
}
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