With Visual Studio 2012 I created a JavaScript Blank App, added a global variable in js/default.js:
var mylabel = "my label";
and I called
WinJS.Binding.processAll();
at the end of app.onactivated.
Then I added two AppBarCommands in default.html:
<button data-win-control="WinJS.UI.AppBarCommand"
data-win-bind="label: mylabel">
</button>
<button data-win-control="WinJS.UI.AppBarCommand"
data-win-bind="innerText: mylabel">
</button>
The first binding does nothing, the second one shows the text "my label" instead of the button. How can I databind the button label ?