Improve wildcard check

Author: muan

include-fragment-element.js

@@ -37,6 +37,10 @@ function getData(el) {
   }
 }
 
+function isWildcard(accept) {
+  return accept && !!accept.split(',').find(x => x.match(/^\s*\*\/\*/))
+}
+
 export default class IncludeFragmentElement extends HTMLElement {
   constructor() {
     super()
@@ -127,7 +131,7 @@ export default class IncludeFragmentElement extends HTMLElement {
           throw new Error(`Failed to load resource: the server responded with a status of ${response.status}`)
         }
         const ct = response.headers.get('Content-Type')
-        if (this.accept !== '*/*' && (!ct || !ct.match(this.accept ? this.accept : /^text\/html/))) {
+        if (!isWildcard(this.accept) && (!ct || !ct.match(this.accept ? this.accept : /^text\/html/))) {
           throw new Error(`Failed to load resource: expected ${this.accept || 'text/html'} but was ${ct}`)
         }
         return response