habitica/website/common/script/libs/extendableBuiltin.js

// TODO use https://babeljs.io/docs/en/babel-plugin-transform-classes
// Babel 6 doesn't support extending native class (Error, Array, ...)
// This function makes it possible to extend native classes with the same results as Babel 5
export default function extendableBuiltin (klass) {
  function ExtendableBuiltin () {
    klass.apply(this, arguments); // eslint-disable-line prefer-rest-params
  }
  ExtendableBuiltin.prototype = Object.create(klass.prototype);
  Object.setPrototypeOf(ExtendableBuiltin, klass);

  return ExtendableBuiltin;
}