Nativescript plugin with extended WebView functionality
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Latest commit 77c4ca6 Jan 17, 2019


Extended WebView for NativeScript which adds "x-local"-custom-scheme for loading local-files, handle events between WebView and NativeScript, JavaScript execution, injecting CSS and JS-files. Supports Android 19+ and iOS9+.


  • Adds a custom-scheme handler for x-local:// to the webview for loading of resources inside the webview.
    • Note: For iOS 11+ WKWebView is used, but for iOS <11 UIWebView is used
  • Adds support for capturing URLs.
    • This allows the app to open external links in an external browser and handle tel-links
  • Added functions like:
    • executeJavaScript(code: string) for executing JavaScript-code and getting result.
    • executePromise(code: string) for calling promises and getting the result.
    • getTitle() returns document.title.
  • Two-Way event listeners between NativeScript and WebView
    • From NativeScript to WebView
    • From WebView to NativeScript
  • Adds functions to inject css- and javascript-files.
    • Into the current page.
    • Auto-injected on page load.
  • Polyfills:
    • Promise
    • Fetch API (overrides Native API on Android to support x-local:// and file://)
  • Supports:
    • Android 19+
    • iOS 9+


Describe your plugin installation steps. Ideally it would be something like:

tns plugin add @nota/nativescript-webview-ext

Angular support

Import WebViewExtModule from @nota/nativescript-webview-ext/angular and add it to your NgModule.

Vue support

Import @nota/nativescript-webview-ext/vue in your app entry file (llikely app.js or main.js).

This registers the element WebViewExt for Vue.



In order to intercept requests for the custom scheme, we use UIWebView for iOS 9 and 10 and WKWebView for iOS 11+.

iOS 11 added support for setting a WKURLSchemeHandler on the WKWebView. Prior to iOS 11 there isn't support for intercepting the URL with WKWebView, so we use a custom NSURLProtocol + UIWebView.


The custom NSURLProtocol used with UIWebView is shared with all instances of the WebViewExt, so mapping x-local://local-filename.js => file://app/full/path/local-filename.js is shared between them.


NativeScript View

Property Value Description
readonly isUIWebView true / false Is the native webview an UIWebView? True if iOS <11
readonly isWkWebView true / false Is the native webview an WKWebView? True if iOS >=11
src Load src
autoInjectJSBridge true / false Should the window.nsWebViewBridge be injected on loadFinishedEvent? Defaults to true
 debugMode true / false Android: Enable chrome debugger for webview on Android. Note: Applies to all webviews in App
scrollBounce true / false iOS: Should the scrollView bounce? Defaults to true.
builtInZoomControls true / false Android: Is the built-in zoom mechanisms being used
displayZoomControls true / false Android: displays on-screen zoom controls when using the built-in zoom mechanisms
 databaseStorage  true / false Android: Enaable/Disabled database storage API. Note: It affects all webviews in the process.
 domStorage  true / false Android: Enaable/Disabled DOM Storage API. E.g localStorage
supportZoom:  true / false Android: should the webview support zoom
 cacheMode default / no_cache / cache_first / cache_only Android: Set caching mode.
Function Description
loadUrl(src: string): Promise Open a URL and resolves a promise once it has finished loading.
registerLocalResource(resourceName: string, path: string): void; Map the "x-local://{resourceName}" => "{path}".
unregisterLocalResource(resourceName: string): void; Removes the mapping from "x-local://{resourceName}" => "{path}"
getRegisteredLocalResource(resourceName: string): void; Get the mapping from "x-local://{resourceName}" => "{path}"
loadJavaScriptFile(scriptName: string, filepath: string) Inject a javascript-file into the webview. Should be called after the loadFinishedEvent
loadStyleSheetFile(stylesheetName: string, filepath: string, insertBefore: boolean) Loads a CSS-file into document.head. If before is true, it will be added to the top of document.head otherwise as the last element
loadJavaScriptFiles(files: {resourceName: string, filepath: string}[]) Inject multiple javascript-files into the webview. Should be called after the loadFinishedEvent
loadStyleSheetFiles(files: {resourceName: string, filepath: string, insertBefore: boolean}[]) Loads multiple CSS-files into the document.head. If before is true, it will be added to the top of document.head otherwise as the last element
autoLoadJavaScriptFile(resourceName: string, filepath: string) Register a JavaScript-file to be injected on loadFinishedEvent. If a page is already loaded, the script will be injected into the current page.
autoLoadStyleSheetFile(resourceName: string, filepath: string, insertBefore?: boolean) Register a CSS-file to be injected on loadFinishedEvent. If a page is already loaded, the CSS-file will be injected into the current page.
autoExecuteJavaScript(scriptCode: string, name: string) Execute a script on loadFinishedEvent. The script can be a promise
executeJavaScript(scriptCode: string) Execute JavaScript in the webpage. Note: scriptCode should be ES5 compatible, or it might not work on 'iOS < 11'
executePromise(scriptCode: string, timeout: number = 500) Run a promise inside the webview. Note: Executing scriptCode must return a promise.
emitToWebView(eventName: string, data: any) Emit an event to the webview. Note: data must be stringify'able with JSON.stringify or this throws an exception.
getTitle() Returns a promise with the current document title.


Event Description
'shouldOverideUrlLoading' Raised before the webview requests an URL. Can cancelled by setting args.cancel = true in the ShouldOverideUrlLoadEventData
'loadStarted' Raised when a loadStarted event occurs. args is an LoadStartedEventData
'loadFinished' Raised when a loadFinished event occurs. args is an LoadFinishedEventData
Events emitted from the webview Raised when nsWebViewBridge.emit(...) is called inside the webview. args in an WebViewEventData


Inside the WebView we have the nsWebViewBridge for sending events between the NativeScript-layer and the WebView. Note: The bridge will only be available DOMContentLoaded or onload inside the WebView.

Function Description
window.nsWebViewBridge.on(eventName: string, cb: (data: any) => void) Registers handlers for events from the native layer. string, cb?: (data: any) => void) Deregister handlers for events from the native layer. 
window.nsWebViewBridge.emit(eventName: string, data: any) Emits event to NativeScript layer. Will be emitted on the WebViewExt as any other event, data will be a part of the WebViewEventData-object 

Possible features to come:

  • Cookie helpers?
  • Setting view-port metadata?
  • Share cache with native-layer?


  • Settings
    • Cache mode?
    • AppCache and AppCAchePath?
    • User agent?


  • Optionas for native scrolllView.
  • Disable/Enable scroll bounce.
  • UIWebView? scalesPageToFit.


Apache License Version 2.0, January 2004

About Nota

Nota is the Danish Library and Expertise Center for people with print disabilities. To become a member of Nota you must be able to document that you cannot read ordinary printed text. Members of Nota are visually impaired, dyslexic or otherwise impaired. Our purpose is to ensure equal access to knowledge, community participation and experiences for people who're unable to read ordinary printed text.