This chapter offers a quite exhaustive description of symbols; just a few, less frequently used and less well-known symbols have been omitted. The complete list of all well-known symbols is available in Mozilla documentation here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol.
In case a Promise polyfill is needed because promises must also be used in old browsers, the es6-promise NPM package is a good choice. More information regarding the npm directory can be found here: https://www.npmjs.com/package/es6-promise.
This chapter describes the more common applications of the fetch API. An exhaustive description of all available options can be found in Mozilla documentation here: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API. Since fetch doesn't have complete support in all browsers, a polyfill is usually...
