Fix spurious spec failure on IE10 by treating IE10 as a standard browser

spec/defaultBindings/valueBehaviors.js

@@ -323,10 +323,13 @@ describe('Binding: Value', {
         value_of(dropdown.selectedIndex).should_be(2);
     },
 
-    'On IE, should respond exactly once to "propertychange" followed by "blur" or "change" or both': function() {
-        var isIE = navigator.userAgent.indexOf("MSIE") >= 0;
+    'On IE < 10, should respond exactly once to "propertychange" followed by "blur" or "change" or both': function() {
+        // This spec describes the awkward choreography of events needed to detect changes to text boxes on IE < 10,
+        // because it doesn't fire regular "change" events when the user selects an autofill entry. It isn't applicable
+        // on IE 10+ or other browsers, because they don't have that problem with autofill.
+        var isOldIE = JSSpec.Browser.IEVersion && JSSpec.Browser.IEVersion < 10;
 
-        if (isIE) {
+        if (isOldIE) {
             var myobservable = new ko.observable(123).extend({ notify: 'always' });
             var numUpdates = 0;
             myobservable.subscribe(function() { numUpdates++ });

spec/lib/JSSpec.extensions.js

@@ -62,4 +62,18 @@ JSSpec.prepareTestNode = function() {
     testNode = document.createElement("div");
     testNode.id = "testNode";
     document.body.appendChild(testNode);
-};
+};
+
+// Note that, since IE 10 does not support conditional comments, the following logic only detects IE < 10.
+// Currently this is by design, since IE 10+ behaves correctly when treated as a standard browser.
+// If there is a future need to detect specific versions of IE10+, we will amend this.
+JSSpec.Browser.IEVersion = (function() {
+    var version = 3, div = document.createElement('div'), iElems = div.getElementsByTagName('i');
+
+    // Keep constructing conditional HTML blocks until we hit one that resolves to an empty fragment
+    while (
+        div.innerHTML = '<!--[if gt IE ' + (++version) + ']><i></i><![endif]-->',
+        iElems[0]
+    );
+    return version > 4 ? version : undefined;
+}());

src/utils.js

@@ -16,6 +16,9 @@ ko.utils = new (function () {
     var eventsThatMustBeRegisteredUsingAttachEvent = { 'propertychange': true }; // Workaround for an IE9 issue - https://github.com/SteveSanderson/knockout/issues/406
 
     // Detect IE versions for bug workarounds (uses IE conditionals, not UA string, for robustness)
+    // Note that, since IE 10 does not support conditional comments, the following logic only detects IE < 10.
+    // Currently this is by design, since IE 10+ behaves correctly when treated as a standard browser.
+    // If there is a future need to detect specific versions of IE10+, we will amend this.
     var ieVersion = (function() {
         var version = 3, div = document.createElement('div'), iElems = div.getElementsByTagName('i');