A small library for transforming TypeScript code into JavaScript code in the least destructive way possible. This library exports a single function whose purpose is to preserve everything else about the code except for the actual TypeScript syntax itself. As a result, things like decorators and class fields should pass straight through without being transformed in any way.

import { removeTypes } from 'remove-types';

const original = `
type AnimalType = 'cat' | 'dog';

// An interface for animals (this comment should be removed when transformed)
interface Animal {
  type: AnimalType;
  name: string;
  age: number;
}

class Cat implements Animal {
  type: AnimalType = 'cat';
  name: string;
  age: number;

  constructor(name: string, age: number) {
    // This is the name of the animal (this comment should stay)
    this.name = name;
    this.age = age;
  }
}
`;

console.log(await removeTypes(original));

/*
class Cat {
  type = 'cat';

  constructor(name, age) {
    // This is the name of the animal (this comment should stay)
    this.name = name;
    this.age = age;
  }
}
*/

• code: A string containing TypeScript code

• prettierConfig:

  • defaults to true
  • By default, removeTypes will run Prettier with a very basic config on the transformed code before returning it. This allows us to clean up some of the "low-hanging" fruit leftover from the Babel transform, e.g. newlines at the beginning or end of the file.
  • If you'd prefer to not run Prettier at all, passing false will bypass the Prettier pass entirely.
  • If you'd prefer to use your own Prettier configuration, you can pass an object containing Prettier configuration options and removeTypes will use it instead.

• returns Promise<string>: a string containing the transformed JavaScript output.

This library is heavily indebted to cyco130/detype and began as an extraction and refactor of one of its core functions.