fix: use fetch and Headers fallbacks

Author: Gozala

src/http/fetch.browser.js

@@ -2,7 +2,7 @@
 /* eslint-env browser */
 
 const { TimeoutError, AbortError } = require('./error')
-const Response = require('./response')
+const { Request, Response, Headers, fetch } = require('./fetch.polyfill')
 
 /**
  * @typedef {RequestInit & ExtraFetchOptions} FetchOptions

src/http/fetch.polyfill.js

@@ -0,0 +1,22 @@
+'use strict'
+
+/* eslint-env browser */
+
+// JSDOM has `XMLHttpRequest` but it does not have a `fetch` or `Response` so
+// we workaround by pulling in node-fetch.
+// See: https://github.com/jsdom/jsdom/issues/1724
+exports.fetch = typeof fetch === 'function'
+  ? fetch
+  : require('node-fetch')
+
+exports.Response = typeof Response === 'function'
+  ? Response
+  : require('node-fetch').Response
+
+exports.Request = typeof Request === 'function'
+  ? Request
+  : require('node-fetch').Response
+
+exports.Headers = typeof Headers === 'function'
+  ? Headers
+  : require('node-fetch').Headers