网页中屏蔽删除键起到后退的作用

$(document).ready(function () {
    document.onkeydown = kp;
    function kp(e) {
        e = window.event || e;
        var obj = e.target || e.srcElement; //获取事件源         
        var k = e.keyCode || e.which;
        //获取作为判断条件的事件类型     
        var vReadOnly = obj.getAttribute('readonly');
        var vEnabled = obj.getAttribute('enabled');
        if (k == 8 && (vReadOnly || vEnabled)) {
            return false;
        }
    }
});