获取页面回退状态

function isBack(){
        var bInfo=$("body").attr("id");
        if(bInfo=="detail"){
            pushHistory();
            window.addEventListener("popstate", function(e) {
                $("#video_bg").css("display","block");
                $("#video_box").html("").css("display","none");
                $("#tc_sp").css("display","none");
            }, false);
            function pushHistory() {
                var state = {
                title: "title",
                url: "#"
            };
            window.history.pushState(state, "title", "#");
            }
        }
    }