禁掉浏览器的后退事件（键盘上的后退）

 //禁用浏览器的backspace默认回退事件
            	document.onkeypress=function (e){
            	    var ev = e || window.event;//获取event对象
            	    var obj = ev.target || ev.srcElement;//获取事件源
            	    var t = obj.type || obj.getAttribute(‘type‘);//获取事件源类型
            	    if(ev.keyCode == 8 && t != "password" && t != "text" && t != "textarea" && t != "number"){
            	        return false;
            	    }
            	}
            	document.onkeydown=function (e){
            	    var ev = e || window.event;//获取event对象
            	    var obj = ev.target || ev.srcElement;//获取事件源
            	    var t = obj.type || obj.getAttribute(‘type‘);//获取事件源类型
            	    if(ev.keyCode == 8 && t != "password" && t != "text" && t != "textarea" && t != "number"){
            	        return false;
            	    }
            	}
            	var counter = 0;
                if (window.history && window.history.pushState) {
                                 $(window).on(‘popstate‘, function () {
                                                window.history.pushState(‘forward‘, null, ‘#‘);
                                                window.history.forward(1);
                                    });
                  }
     
                  window.history.pushState(‘forward‘, null, ‘#‘); //在IE中必须得有这两行
                  window.history.forward(1);