fix(bootstrap): missing check for duplicated google analytics script

closes #110

Author: MatteoGabriele

src/bootstrap.js

@@ -1,4 +1,4 @@
-import { loadScript } from './helpers'
+import { loadScript, shouldGaLoad } from './helpers'
 import config, { update } from './config'
 import createTrackers from './create-trackers'
 import collectors from './collectors'
@@ -20,10 +20,11 @@ export default () => {
     )
   }
 
-  if (!window.ga || !disableScriptLoader) {
+  if (shouldGaLoad() && (!window.ga || !disableScriptLoader)) {
     loadScript(resource).catch(() => {
       console.error(
-        `[vue-analytics] An error occured trying to load ${resource}. Please check your connection.`
+        `[vue-analytics] An error occured trying to load ${resource}. Please check your connection ` +
+        `or if you have any Google Analytics blocker installed in your browser.`
       )
     })
   }

src/helpers.js

@@ -11,7 +11,7 @@ export function loadScript (url) {
     script.charset = 'utf8'
 
     head.appendChild(script)
-    
+
     script.onload = resolve
     script.onerror = reject
   })
@@ -40,16 +40,21 @@ export function merge (obj, src) {
   return obj
 }
 
-export function hasGoogleScript () {
+export function hasScript () {
   const scriptTags = Array.prototype.slice.call(
     document.getElementsByTagName('script')
   ).filter(script => {
-    return script.src.indexOf('analytics') !== -1
+    return (script.src.indexOf('analytics') !== -1) ||
+      (script.src.indexOf('gtag') !== -1)
   })
 
   return scriptTags.length > 0
 }
 
+export function shouldGaLoad () {
+  return !(config.checkDuplicatedScript && hasScript())
+}
+
 export function getTracker (tracker) {
   return tracker.name || tracker.replace(/-/gi, '')
 }