Ionic Info
Ionic:
ionic (Ionic CLI) : 4.1.0 (/usr/lib/node_modules/ionic)
Ionic Framework : @ionic/angular 4.0.0-beta.3
@angular-devkit/core : 0.7.3
@angular-devkit/schematics : 0.7.3
@angular/cli : 6.1.3
@ionic/ng-toolkit : 1.0.6
@ionic/schematics-angular : 1.0.4
Cordova:
cordova (Cordova CLI) : 8.0.0
Cordova Platforms : android 7.0.0
Cordova Plugins : cordova-plugin-ionic-keyboard 2.1.2, cordova-plugin-ionic-webview 2.0.2, (and 4 other plugins)
System:
Android SDK Tools : 26.0.1
NodeJS : v10.8.0 (/usr/bin/node)
npm : 6.3.0
OS : Linux 4.4
Environment:
ANDROID_HOME : /opt/android
Describe the Bug
Ionic v4 won't work with older Android System WebViews.
Additional Context
We are currently testing and developing with Ionic v4 on devices with older web views.
One of them is a Android N (7.1.2) device without any Google Mobile Services (GMS). So we have to use the standard Android System WebView (version 52.0.2743.100). When running the _Ionic Blank Starter_ build with _Cordova_ we are getting following result:
Uncaught SyntaxError: Unexpected token function vendor.js:65052

Unfortunately the manufacturer of the device says we can't upgrade to more recent version.
The other device is an Android L (5.1.1) which is also shipped without GMS. Here we have an Android System WebView version of 55.0.2883.91 with following result:

The app is successfully loaded, but the icon in the button on the top right is not shown.
<ion-header>
<ion-toolbar>
<ion-title>
Ionic Blank
</ion-title>
<ion-buttons slot="end">
<ion-button>
<ion-icon slot="icon-only" name="person"></ion-icon>
</ion-button>
</ion-buttons>
</ion-toolbar>
</ion-header>
<ion-content padding>
The world is your oyster.
<p>If you get lost, the <a target="_blank" href="https://ionicframework.com/docs">docs</a> will be your guide.</p>
</ion-content>
Everything works while runinng on a more recent webview version (68.0.3440.91):

Maybe the problem is related to this issue #15191?
Confirm above issues.
Just created new project and i had the same issue
Uncaught SyntaxError: Unexpected token function
Ionic:
ionic (Ionic CLI) : 4.1.1 (C:\Users\taran\AppData\Roaming\npm\node_modules\ionic)
Ionic Framework : @ionic/angular 4.0.0-beta.3
@angular-devkit/core : 0.7.5
@angular-devkit/schematics : 0.7.5
@angular/cli : 6.1.5
@ionic/ng-toolkit : 1.0.7
@ionic/schematics-angular : 1.0.5
Cordova:
cordova (Cordova CLI) : 8.0.0
Cordova Platforms : android 7.0.0
Cordova Plugins : not available
System:
Android SDK Tools : 26.1.1 (C:\Users\taran\AppData\Local\Android\Sdk)
NodeJS : v10.9.0 (C:\Program Files\nodejs\node.exe)
npm : 6.2.0
OS : Windows 10
ASW Android System Webview 52.0.2743.100 neither runs. Is there going to be a solution for old ASW?
Related to #15438
Thanks for the issue! This issue is being locked to prevent comments that are not relevant to the original issue. If this is still an issue with the latest version of Ionic, please create a new issue and ensure the template is fully filled out.
Most helpful comment
Confirm above issues.