js表头标题固定

//表头跟踪固定（按钮与表头）
var trObj = $("#zdy_id").find("tr:eq(3)");//自定义zdy_id，处于第3行
var trObjChild = $(trObj).children();
var topValue = 0;

var trObj_hj = $("#zdy_id").find("tr:eq(4)");
var trObjChild_hj = $(trObj_hj).children();

trObjChild.css({ position: "relative", "z-Index": 999 });
trObjChild_hj.css({ position: "relative", "z-Index": 999 });
$("#scrollDiv").scroll(function () {//默认
    topValue = $(this).attr("scrollTop");
    if (topValue <= 21) {
        topValue = 0;
    }
    else {
        topValue = topValue - 110;//这个高度可自己设置
    }
    setTimeout(function () {
        trObjChild.css({ top: topValue + "px" });
        trObjChild_hj.css({ top: topValue + "px" });
    }, 0);

});