I've seen the question come up on occasion about using WinJS within a webview. This is entirely supported, and has been since the introduction of WinJS–the library always checks whether WinRT is present and adjusts itself accordingly. For example, if WinRT is available, then it will use WinRT app data for saving its settings; if WinRT isn't available, it uses standard HTML5 APIs instead.

This strategy wisely foresaw the day when WinJS was licensed for use in web page. This wasn't originally the case (as the copyright headers in the WinJS files made clear), but with WinJS going open source in April 2014, WInJS can be used anywhere.

When using WinJS, and especially WinJS controls, inside a webview or web page, it's important to remember steps that are included by default within the Windows app templates, most notable the step of calling WinJS.UI.processAll. That is, when you create a new Windows app, the templates in Visual Studio supply the following default activation code:

var app = WinJS.Application;
var activation = Windows.ApplicationModel.Activation;

app.onactivated = function (args) {
    if (args.detail.kind === activation.ActivationKind.launch) {
        if (args.detail.previousExecutionState !== activation.ApplicationExecutionState.terminated) {
            // TODO: This application has been newly launched. Initialize
            // your application here.
        } else {
            // TODO: This application has been reactivated from suspension.
            // Restore application state here.

Clearly, if you're using WinJS outside of an app, then the Windows.ApplicationModel.Activation namespace won't mean anything, so naturally you'll delete all the code inside the onactivated handler here. But if you delete WinJS.UI.processAll then none of your WinJS controls will show up. This can be confusing and might lead to the idea that WinJS doesn't work in a webview. But it does, because in the end WinJS is just a JavaScript library using standard HTML5/DOM to do its work. So just make sure that somewhere you have a line like this:



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