fallback EventTarget constructor for Safari <= 13 and IE

EventTarget.js

const Original = self.EventTarget;

let availabilityOfEventTargetConstructor = true;
try {
  new Original();
} catch {
  availabilityOfEventTargetConstructor = false;
}

/** @type {{ new(): EventTarget, prototype: EventTarget }} */
export let EventTarget;

if (availabilityOfEventTargetConstructor) {
  EventTarget = Original;
} else {
  /** @type {{ new (): EventTarget, prototype: EventTarget }} */
  // @ts-ignore
  const FallbackEventTarget = function EventTarget() {
    if (new.target === undefined) {
      throw new TypeError("Constructor EventTarget requires 'new'");
    }

    /** @type {EventTarget} */
    const fallback = self?.document.createDocumentFragment() ?? new FileReader();
    Object.setPrototypeOf(fallback, Original.prototype);

    return fallback;
  }
  FallbackEventTarget.prototype = Original.prototype;

  EventTarget = FallbackEventTarget;
}

以前のやつ。
https://gist.github.com/petamoriken/bb99ca136bc663d3c6ac

IE のためには特にこれが必要。
https://babeljs.io/docs/en/next/babel-plugin-transform-new-target.html

こちらの記事を参考にしました。
http://var.blog.jp/archives/81507050.html