refactor: extractUrl + add JS docs

Co-authored-by: Jordan Porter <insomniacrampage@hotmail.com>

Author: ptang-nr

src/common/url/extract-url.js

@@ -5,13 +5,13 @@
 import { globalScope } from '../constants/runtime'
 import { gosNREUMOriginals } from '../window/nreum'
 
-export function extractUrl (target) {
-  if (typeof target === 'string') {
-    return target
-  } else if (typeof target === 'object' && target instanceof gosNREUMOriginals().o.REQ) {
-    return target.url
-  } else if (globalScope?.URL && typeof target === 'object' && target instanceof URL) {
-    return target.href
-  }
-  return undefined
+/**
+ * Extracts a URL from various target types.
+ * @param {string|Request|URL} target - The target to extract the URL from. It can be a string, a Fetch Request object, or a URL object.
+ * @returns {string|undefined} The extracted URL as a string, or undefined if the target type is not supported.
+ */
+export function extractUrl(target) {
+  if (typeof target === 'string')  return target
+  else if (target instanceof gosNREUMOriginals().o.REQ) return target.url
+  else if (globalScope?.URL && target instanceof URL) return target.href
 }