Detect ClickOnce support of browser

README

Detect if ClickOnce is (or rather: might be) supported by the browser.
This is partly based on https://gist.github.com/adunkman/2371101.
If the userAgent string does not contain a .NET feature hint,
we settle for everything that looks like an IE, because .NET 
is installed nearly everywhere nowadays.

It might also be a good idea to check for the X-ClickOnceSupport 
header on the server side.

clickonce.js

(function () {
    var isMimeSupported = function (desiredMime) {
        var mimes = window.navigator.mimeTypes;

        for (var i = 0; i < mimes.length; i++) {
            if (mimes[i].type == desiredMime) {
                return true;
            }
        }

        return false;
    };

    var isClickOnceSupported = function () {
        var userAgent = window.navigator.userAgent.toLowerCase(),
            hasDotNetFeatureHint = userAgent.indexOf('.NET CLR') >= 0,
            looksLikeIE = userAgent.indexOf('msie') >= 0,
            looksLikeTrident = userAgent.indexOf('trident') >= 0,
            looksLikeEdge = userAgent.indexOf('edge') >= 0;

        return hasDotNetFeatureHint || looksLikeIE 
                || looksLikeTrident || looksLikeEdge 
                || isMimeSupported('application/x-ms-application');
            
    };

    window.hasClickOnceSupport = isClickOnceSupported();
})();