javascript - Javascript：document.getElementbyID(..) 为空或不是对象

Question

我似乎无法理解为什么下面的 javascript 代码给了我 document.getelementbyid 为 null 或不是此行上的对象：行：111。据我所知，所有内容都应该像我声明的所有内容一样工作

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>

score 4 · Accepted Answer

它没有找到您的元素，因为它是在onload加载整个文档时触发的事件中创建的。这意味着它是在执行错误的代码行之后创建的。

score 2 · Accepted Answer

You are calling write_it() in response to the page's load, which fires after the DOM has been fully built and all images and subframes have fully loaded. See the MDN window.onload doc page for more on when onload fires.

However, your getElementById call is firing immediately, as soon as your JavaScript execution evironment is set up, before the DOM is built. Since the write_it function creates the table you're trying to select onload, and it runs after your getElementById call, the table doesn't yet exist when you try to select it.

You should move all of your code into the write_it function so that none of it runs until after the DOM is built.

javascript - Javascript：document.getElementbyID(..) 为空或不是对象

2 回答 2

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