Change Case TS

This library contains functions and types to convert strings, tuple members and property names from one case to another.

While there are plenty of other packages that does the same at runtime, this library is built for full type support.

Useful for converting known models for interacting with external APIs.

Exports

The main export of interest is changeCase. It's parameters are the value which to change, the optional source case, and the target case. If no source case is provided, the library will try and detect it. changeCase works for strings, tuple/array-values, and object keys, in that order. Use changeArrayCase, changeStringCase, or changeKeysCase to specify the target, if needed.

The library also exports types correlating to the functions mentioned above (such as ChangeCase<Value, ToCase, FromCase> etc.), as well as for detecting cases, case names as constants and as literal string types grouped into unions, etc.

Last but not least are the functional variants of the case changing functions: caseChanger, stringCaseChanger, arrayCaseChanger and keysCaseChanger. These can be useful for instance when using transform with Zod schemas (z.object({ FOO_BAR: z.string() }).transform(caseChanger("camelCase"))).

Installation

Setup:

npm install change-case-ts

Code:

import { changeCase } from "change-case-ts";

Setup:

deno add jsr:change-case-ts

Code:

import { changeCase } from "change-case-ts";

Examples

Changing the case of a string literal

import { changeCase } from "change-case-ts";

const stringLiteral = changeCase("howAboutThemApples", "SCREAMING-KEBAB-CASE");

stringLiteral satisfies "HOW-ABOUT-THEM-APPLES";

import { changeCase } from "change-case-ts";

const stringLiteral = changeCase("howAboutThemApples", "SCREAMING-KEBAB-CASE");

stringLiteral satisfies "HOW-ABOUT-THEM-APPLES";

Changing the case of the keys in an object

import { changeCase } from "change-case-ts";

const objectKeys = changeCase(
  {
    some_number: 123,
    an_array: [
      {
        with_a_prop: true,
      },
    ],
  },
  "camelCase",
);

objectKeys satisfies {
  someNumber: 123;
  anArray: [{
    withAProp: true;
  }];
};

import { changeCase } from "change-case-ts";

const objectKeys = changeCase(
  {
    some_number: 123,
    an_array: [
      {
        with_a_prop: true,
      },
    ],
  },
  "camelCase",
);

objectKeys satisfies {
  someNumber: 123;
  anArray: [{
    withAProp: true;
  }];
};

Changing the case of array or tuple values

import { changeCase } from "change-case-ts";

const tuples = changeCase(["foo-bar", "baz", 123], "PascalCase");

tuples satisfies ["FooBar", "Baz", 123];

import { changeCase } from "change-case-ts";

const tuples = changeCase(["foo-bar", "baz", 123], "PascalCase");

tuples satisfies ["FooBar", "Baz", 123];

Changing the keys of objects within an array

// We can't use `changeCase` in this example, as it will try and change any string literal values within the given array instead of the keys in the object items, so we specifically use `changeKeysCase` instead to remove the ambiguity.

import { changeKeysCase } from "change-case-ts";

type Response = Array<{ foo_bar: string }>;

const response: Response = await fetch(
  "https://www.example.com",
).then((res) => res.json());

const result = changeKeysCase(response, "camelCase");

result satisfies Array<{ fooBar: string }>;

// We can't use `changeCase` in this example, as it will try and change any string literal values within the given array instead of the keys in the object items, so we specifically use `changeKeysCase` instead to remove the ambiguity.

import { changeKeysCase } from "change-case-ts";

type Response = Array<{ foo_bar: string }>;

const response: Response = await fetch(
  "https://www.example.com",
).then((res) => res.json());

const result = changeKeysCase(response, "camelCase");

result satisfies Array<{ fooBar: string }>;

Loading a dotenv-file and parsing with Zod

Setup:

npm install --save-dev @types/node
npm install dotenv zod change-case-ts
echo "MY_ENV_VAR='Hello, world!'" >> .env

Code:

import "dotenv/config";
import { caseChanger } from "change-case-ts";
import z from "zod";

const envSchema = z.object({
  MY_ENV_VAR: z.string(),
});

const camelCaseEnvSchema = envSchema.transform(
  caseChanger("camelCase"),
);

const env = camelCaseEnvSchema.parse(process.env);

env satisfies {
  myEnvVar: string;
};

console.log(env.myEnvVar);

Setup:

deno add npm:zod jsr:@std/dotenv jsr:change-case-ts
echo "MY_ENV_VAR='Hello, world!'" >> .env

Code:

import "@std/dotenv/load";
import { caseChanger } from "change-case-ts";
import z from "zod";

const envSchema = z.object({
  MY_ENV_VAR: z.string(),
});

const camelCaseEnvSchema = envSchema.transform(
  caseChanger("camelCase"),
);

const env = camelCaseEnvSchema.parse(Deno.env.toObject());

env satisfies {
  myEnvVar: string;
};

console.log(env.myEnvVar);

Supported cases

The following cases are currently supported:

• Non-delimited cases:
  • lowercase
  • UPPERCASE
• Capitalization-delimited cases:
  • camelCase
  • PascalCase
• Symbol-delimited cases:
  • snake_case
  • UPPER_SNAKE_CASE (a.k.a. SCREAMING_SNAKE_CASE and CONSTANT_CASE)
  • kebab-case
  • UPPER-KEBAB-CASE (a.k.a. SCREAMING-KEBAB-CASE)

Missing a case? File an issue on GitHub