Table 固定标题列

<div style="position:fixed;top:0;left:0;width:100%;z-index:99;background-color:#fff;padding-left:10px;display:none" id="mytitle">
    <table id="titletable" class="table2" style="width:99%;text-align:center;">
    </table>
</div>

settable();
    function settable() {
        var fro = document.getElementsByClassName("fro");
        var table = document.getElementById("titletable");
        var wheit = 0;
        var len = fro.length
        for (var i = 0; i < len; i++) {
            
            var tr = document.createElement("tr");
            for (var k = 0; k < fro[i].childNodes.length; k++) {
                var td = document.createElement("td");
                var child = fro[i].childNodes[k]
                if (child.innerHTML) { 
                    var div=document.createElement("div");
                    div.innerHTML = child.innerHTML;
                    td.rowSpan = child.rowSpan;
                    td.colSpan = child.colSpan;
                   
                    console.log(child.offsetWidth);
                    div.style.width = child.offsetWidth-9 + "px";
                    td.appendChild(div);
                    tr.appendChild(td);
                    if (i == 0) {
                        wheit += child.offsetWidth;
                    }
                }
            }
            table.appendChild(tr);
        }
        document.getElementById("titletable").style.width = wheit + "px";
        console.log(table);
    }
    
    function fixTabel()
    {
        var sl = -Math.max(document.body.scrollLeft, document.documentElement.scrollLeft);
        var fro = document.getElementsByClassName("fro");
        if (fro[0].getBoundingClientRect().top < 0) {
            document.getElementById("mytitle").style.display = "";
        }
        else {
            document.getElementById("mytitle").style.display = "none";
        }
    }
    function getTop(e) {
        var offset = e.offsetTop;
        if (e.offsetParent != null) offset += getTop(e.offsetParent);
        return offset;
    }