superflected/src/camelize.ts

A port of ActiveSupport's inflector to Node.js

import { inflections } from "./Inflector";
import type { AhoCorasick } from "./ahoCorasick";
import { cacheable } from "./cacheable";
import { capitalize } from "./capitalize";

const separators = /(?:_|(\/))([a-z\d]*)/gi;

export const camelize = cacheable(
  (term: string, uppercaseFirstLetter = true) => {
    const inflector = inflections();

    let result: string = term;

    if (uppercaseFirstLetter) {
      const startAcronym = findLongestStartAcronym(inflector.lowerAcronymMatcher, term);
      if (startAcronym) {
        result = inflector.lowerToAcronyms[startAcronym] + result.slice(startAcronym.length);
      } else {
        result = term.charAt(0).toUpperCase() + term.slice(1);
      }
    } else {
      const startAcronym = findLongestStartAcronym(inflector.casedAcronymMatcher, term);
      if (startAcronym) {
        result = startAcronym.toLowerCase() + result.slice(startAcronym.length);
      } else {
        result = term.charAt(0).toLowerCase() + term.slice(1);
      }
    }

    result = result.replace(separators, (_match, separator, word) => {
      word = inflector.lowerToAcronyms[word] ?? capitalize(word);
      if (separator) {
        return separator + word;
      } else {
        return word;
      }
    });

    return result;
  },
  (term, uppercaseFirstLetter) => `${term}-${uppercaseFirstLetter}`
);

const findLongestStartAcronym = (matcher: AhoCorasick | null, word: string) => {
  if (!matcher) return null;

  const results = matcher.search(word, undefined, true);
  if (results.length > 0) {
    return results[0][1];
  }
  return null;
};