Fetch JSONP using vanilla javascript

fetchjsonp.js

/**
 * source: [Create GUID / UUID in JavaScript?, broofa]{@link https://stackoverflow.com/a/2117523}
 */
export function uuidv4() {
  return ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
    (
      c ^
      (crypto.getRandomValues(new Uint8Array(1))[0] & (15 >> (c / 4)))
    ).toString(16),
  );
}

/**
 * Fetch JSONP using vanilla javascript
 * adapted from [Simple JSONP in vanilla JS, @michaelpumo]{@link https://gist.github.com/gf3/132080/110d1b68d7328d7bfe7e36617f7df85679a08968#gistcomment-2090652}
 *
 * @example
 * // returns {"id":"123","user":"John"}
 * fetchJSONP('https://jsfiddle.net/echo/jsonp?id=123&user=John').then(response => {
 *   response.json().then(data => {
 *      console.log(data);
 *   });
 * });
 */
export function fetchJSONP(url) {
  return new Promise(resolve => {
    let script = document.createElement('script');
    let uuid = uuidv4().replace(/-/g, '');
    let name = `_jsonp_${uuid}`;

    if (url.match(/\?/)) {
      url += `&callback=${name}`;
    } else {
      url += `?callback=${name}`;
    }

    script.src = url;
    window[name] = json => {
      resolve(new Response(JSON.stringify(json)));
      script.remove();
      delete window[name];
    };
    document.body.appendChild(script);
  });
}