Angular directive: prevent backspace from acting like the back button

backspacedirective

.directive('backSpaceNotBackButton', [function(){
    return {
        restrict: 'A',
        link: function(scope, element, attrs){
            // This will stop backspace from acting like the back button
            $(element).keydown(function (e) {
                var elid = $(document.activeElement)
                    .filter(
                        "input:not([type], [readonly]),"+
                        "input[type=text]:not([readonly]), " +
                        "input[type=password]:not([readonly]), " +
                        "input[type=search]:not([readonly]), " +
                        "input[type=number]:not([readonly]), " +
                        "input[type=email]:not([readonly]), " +
                        "input[type=date]:not([readonly]), " +
                        "input[type=datetime]:not([readonly]), " +
                        "input[type=datetime-local]:not([readonly]), " +
                        "input[type=month]:not([readonly]), " +
                        "input[type=tel]:not([readonly]), " +
                        "input[type=time]:not([readonly]), " +
                        "input[type=url]:not([readonly]), " +
                        "input[type=week]:not([readonly]), " +
                        "textarea")[0];
                if (e.keyCode === 8 && !elid) {
                    return false;
                }
            });
        }
    }
}])

could you please explain how to use. i am new in angulrjs

thanks in advance
AKD