window.addEventListener('popstate', function(event) {
    // Do here what you want to do when click (back) on browser!

    // for example here is code to catch the current hash:
    var hashLocation = location.hash;
    var hashSplit = hashLocation.split("#!/");
    var hashName = hashSplit[1];
    if(hashName != '')
    {
        alert('gotcha! the back hash name was: ('+hashName+')');
    }
});