Question

我似乎无法想象为什么下面的javascript代码给我document.getelementbyid为null或不是此行上的对象：第111行。据我所知，所有人都应该按照我所宣布的一切工作

var rows = document.getElementById("mstrTable").getElementsByTagName("tr");

这是完整的代码：

    <html>
<head>
    <title>Scrolling Data Grid</title>
<style>
/* ==================================================================== */
/* SCROLLING DATA GRID - IE ONLY!                                       */
/* ==================================================================== */
/* 
Tables inside a scrollingdatagrid should have:
 1. border-collapse:separate
 2. No border or margin
 3. Background colors on all cells to avoid bleed-thru on scroll
 4. cellspacing="0" on the <table> tag itself
*/
DIV.scrollingdatagrid {
    overflow-x:auto;
    overflow-y:auto;
    position:relative;
    padding:0px;
}
DIV.scrollingdatagrid TABLE {
    width : 98.7%; /* Make room for scroll bar! */
    margin:0px;
    border:0px;
    border-collapse:separate;
}
DIV.scrollingdatagrid TABLE TR .locked, DIV.scrollingdatagrid TABLE THEAD TR, DIV.scrollingdatagrid TABLE TFOOT TR {
    position:relative;
}
/* OffsetParent of the TR is the DIV because it is position:relative */
DIV.scrollingdatagrid TABLE THEAD TR {
    top:expression(this.offsetParent.scrollTop);
}


/* Make the z-index values very clear so overlaps happen as expected! */
DIV.scrollingdatagrid TD, DIV.scrollingdatagrid TH { z-index:1; }
DIV.scrollingdatagrid TD.locked, DIV.scrollingdatagrid TH.locked { z-index:2; }
DIV.scrollingdatagrid THEAD TR, DIV.scrollingdatagrid TFOOT TR { z-index:3; }
DIV.scrollingdatagrid THEAD TR TH.locked { z-index:4; }
</style>


<script type="text/javascript">
window.onload = function(){ write_it() }

function write_it() {

var cn      =   new ActiveXObject("ADODB.Connection")
var rs      =   new ActiveXObject("ADODB.Recordset")
var dbFile  =   "imts.mdb"
var dbPath  =   "G:\\AS\\Asf\\ASF\\IMTS\\V8\\database\\"

var mySQL   = "SELECT * FROM tbl_imts WHERE [FILE NUMBER] LIKE '%99%'"
var html    = ""

cn.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source = " + dbPath + dbFile + "");
rs.Open(mySQL, cn, 1, 3)

html += '<table id="mstrTable" style="table-layout: fixed; font-family: arial; font-size: 9pt;" cellpadding="0" cellspacing="0">\n'
html += '<thead>\n'
html += '<tr>\n'
html += '<th class="locked" style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; height: 30px; width: 20px; color: rgb(102,102,102); background-color: rgb(212,208,200);">#</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(0).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(1).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(2).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(3).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(4).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(5).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(6).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(7).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(8).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(9).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(10).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(11).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(12).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(13).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: 1px solid rgb(128,128,128); padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(14).name + '</th>\n'
html += '<th style="border-bottom: 1px solid rgb(128,128,128); border-top: 1px solid #ffffff; border-left: 1px solid #ffffff; border-right: none; padding-left: 5px; width: 100px; color: rgb(102,102,102); background-color: rgb(212,208,200);">' + rs.fields(15).name + '</th>\n'
html += '</tr>\n'
html += '</thead>\n'

rs.MoveFirst
var i = 0
html += '<tbody>\n'
while (!rs.eof) {
++i
    html    +=  '<tr style="color: rgb(102,102,102)">\n'
    html    +=  '<td class="locked" style="height: 20px; border-right: 1px solid rgb(128,128,128); border-bottom: 1px solid rgb(128,128,128);">'+i+'.</td>\n'
    for (var r = 0; r < rs.fields.count; ++r) {
    if (!rs.fields(r).value) { rs.fields(r).value = "&nbsp;" }
    html    +=  '<td style="border-right: 1px solid rgb(128,128,128); border-bottom: 1px solid rgb(128,128,128); padding-left: 5px; white-space: nowrap; overflow: hidden;">'+rs.fields(r).value+'</td>\n'
    }//end of for
    html    +=  '</tr>\n'
    rs.MoveNext 
    }//end of while
html += '</tbody>\n'
html += '</table>\n'
document.getElementById("p1").innerHTML = html
}
</script>
</head>

<body>

<div id="p1" class="scrollingdatagrid" style="width:800px;height:200px;border:1px solid rgb(128,128,128);"></div>

<script type="text/javascript">
(function() {
var color = "#E1E0D7"
var rows = document.getElementById("mstrTable").getElementsByTagName("tr");
var n = rows.length;
var bgcs = [];
for(var i=0; i<n; ++i) bgcs[i] = rows[i].style.backgroundColor;
//rows[0].style.backgroundColor = color;
function changeColor(e) {
if(!e) e = window.event;
var o = e.target? e.target: e.srcElement;
if (o.tagName == "TH") { return }
while(o.tagName && o.tagName.toLowerCase()!="tr") o = o.parentNode;
for(var i=0; i<n; ++i) {
rows[i].style.backgroundColor = bgcs[i];
if(rows[i]==o) {
                rows[i].style.backgroundColor = color
                }
}
}
if(document.addEventListener) for(var i=0; i<n; ++i) rows[i].addEventListener("click", changeColor, false);
else for(var i=0; i<n; ++i) rows[i].attachEvent("onclick", changeColor);
})();
</script>














</body>
</html>

Answer 1

它找不到您的元素，因为它是在onload事件中创建的，该事件在加载整个文档时触发。这意味着它被创建 AFTER 您的错误代码行被执行。

Answer 2

您正在调用write_it()以响应页面的load，该页面在完全构建DOM并且所有图像和子帧已完全加载后触发。有关onload何时触发的详细信息，请参阅MDN window.onload文档页面。

但是，在构建DOM之前，一旦设置了JavaScript执行环境，您的getElementById调用就会立即触发。由于write_it函数会创建您尝试选择onload的表格，并且它会在您getElementById调用之后运行，因此当您尝试选择该表时，该表格尚不存在。“ / p>

您应该将所有代码移动到write_it函数中，以便在构建DOM之前不会运行任何代码。

Javascript：document.getElementbyID（..）为null或不是对象

2 个答案: