Case Converter

How to use it #

Paste a value, or a list with one value per line. Each line is converted on its own into all ten formats: pasting a column of field names does not merge them into a single identifier.

The formats #

kebab-case and slug look alike but do not do the same thing: the slug treats punctuation as a separator, case conversion removes it. So a/b becomes a-b as a slug and ab in kebab.

Splitting is the real work #

Joining words back together is trivial. Splitting them correctly is where everything happens, and most naive implementations fail on three cases.

// an acronym followed by a word
"HTTPServerError"; // → http, server, error   (not h, t, t, p, server…)
 
// a digit against a letter
"version2Beta"; // → version, 2, beta
 
// accents and an initial capital
"Élément"; // → element   (not e, lement)

Accents must be stripped after splitting: normalising first loses the initial capital, and the word becomes indistinguishable from its lowercase form.

A conversion has to be idempotent #

Re-applying a conversion to its own output must give the same output.

toKebabCase("Create an element"); // "create-an-element"
toKebabCase("create-an-element"); // "create-an-element" — identical

Without that property, a pipeline that converts twice — because two layers apply the same normalisation "just in case" — produces different identifiers on each pass.

Converting an object's keys #

The most common concrete case: an API in snake_case, a front end in camelCase.

const toCamelKeys = (value) => {
  if (Array.isArray(value)) {
    return value.map(toCamelKeys);
  }
 
  if (value === null || typeof value !== "object") {
    return value;
  }
 
  return Object.fromEntries(
    Object.entries(value).map(([key, nested]) => [
      toCamelCase(key),
      toCamelKeys(nested),
    ])
  );
};

Watch the recursion: null is of type object in JavaScript, and without the explicit test the function crashes on the first null value.