Normally, when I use <a href="_URL_"></a> in my metro application, the url is opening in the default web browser. I don't want to do this with anchor, I want to do the same behavior via Javascript and as async. But I don't know how to open the url with default browser. 
Here is my code:
var $aTag = $("<a/>").click(function (event) {
    showYesNoDialog(
        "Do you approve?", 
        "The link will be opened in another window. Do you approve?", 
        "Yes", // Text of yes button
        "No",  // Text of no button
        function () { // Behavior of yes button
            // I tried this but nothing happened.
            window.location.href = _URL_; // Should open in chrome or default web browser
        },
        function () { // Behavior of no button
            // do nothing
        }
    );
});
What I also tried is that:
$("<a href='" + _URL_ + "'></a>").click();
But this didn't work, too.
 
     
    