Add throw error for undefined method on plugins

js/src/scrollspy.js

@@ -277,6 +277,9 @@ const ScrollSpy = (($) => {
         }
 
         if (typeof config === 'string') {
+          if (data[config] === undefined) {
+            throw new Error(`No method named "${config}"`)
+          }
           data[config]()
         }
       })