我正在获取div标签的偏移宽度。下面是代码。
<body>
<div id="marqueeborder" onmouseover="pxptick=0" onmouseout="pxptick=scrollspeed">
<div id="marqueecontent">
<?php
// Original script by Walter Heitman Jr, first published on http://techblog.shanock.com
// List your stocks here, separated by commas, no spaces, in the order you want them displayed:
$stocks = "idt,iye,mill,pwer,spy,f,msft,x,sbux,sne,ge,dow,t";
// Function to copy a stock quote CSV from Yahoo to the local cache. CSV contains symbol, price, and change
function upsfile($stock) { copy("http://finance.yahoo.com/d/quotes.csv?s=$stock&f=sl1c1&e=.csv","stockcache/".$stock.".csv"); }
foreach ( explode(",", $stocks) as $stock ) {
// Where the stock quote info file should be...
$local_file = "stockcache/".$stock.".csv";
// ...if it exists. If not, download it.
if (!file_exists($local_file)) { upsfile($stock); }
// Else,If it's out-of-date by 15 mins (900 seconds) or more, update it.
elseif (filemtime($local_file) <= (time() - 900)) { upsfile($stock); }
// Open the file, load our values into an array...
$local_file = fopen ("stockcache/".$stock.".csv","r");
$stock_info = fgetcsv ($local_file, 1000, ",");
// ...format, and output them. I made the symbols into links to Yahoo's stock pages.
echo "<span class='"stockbox'"><a href='"http://finance.yahoo.com/q?s=".$stock_info[0]."'">".$stock_info[0]."</a> ".sprintf("%.2f",$stock_info[1])." <span style='"";
// Green prices for up, red for down
if ($stock_info[2]>=0) { echo "color: #009900;'">↑"; }
elseif ($stock_info[2]<0) { echo "color: #ff0000;'">↓"; }
echo sprintf("%.2f",abs($stock_info[2]))."</span></span>'n";
// Done!
fclose($local_file);
}
?>
<span class="stockbox" style="font-size:0.6em">Quotes from <a href="http://finance.yahoo.com/">Yahoo Finance</a></span>
</div>
</div>
</body>
下面是 JavaScript 函数，它将被称为页面的 onlaod。
<script type="text/javascript">
// Original script by Walter Heitman Jr, first published on http://techblog.shanock.com
// Set an initial scroll speed. This equates to the number of pixels shifted per tick
var scrollspeed=2;
var pxptick=scrollspeed;
function startmarquee(){
alert("hi");
// Make a shortcut referencing our div with the content we want to scroll
var marqueediv=document.getElementById("marqueecontent");
alert("marqueediv"+marqueediv);
alert("hi"+marqueediv.innerHTML);
// Get the total width of our available scroll area
var marqueewidth=document.getElementById("marqueeborder").offsetWidth;
alert("marqueewidth"+marqueewidth);
// Get the width of the content we want to scroll
var contentwidth=marqueediv.offsetWidth;
alert("contentwidth"+contentwidth);
// Start the ticker at 50 milliseconds per tick, adjust this to suit your preferences
// Be warned, setting this lower has heavy impact on client-side CPU usage. Be gentle.
var lefttime=setInterval("scrollmarquee()",50);
alert("lefttime"+lefttime);
}
function scrollmarquee(){
// Check position of the div, then shift it left by the set amount of pixels.
if (parseInt(marqueediv.style.left)>(contentwidth*(-1)))
marqueediv.style.left=parseInt(marqueediv.style.left)-pxptick+"px";
// If it's at the end, move it back to the right.
else
marqueediv.style.left=parseInt(marqueewidth)+"px";
}
window.onload=startmarquee();
</script>
当 IAM 在服务器上运行上述代码时，IAM 在第 46 行收到 JavaScript 错误作为"需要对象"，也是 alert（"marqueediv"+marqueediv）; 是"marqueedivnull"，在该警报之后，我收到 JavaScript 错误。
我的问题是，div 标签是否未被识别？为什么？所以只有它作为空对象，我该如何解决这个问题？
谢谢。
您立即调用startmarquee并尝试将其返回值（undefined）分配给window.onload。
据推测，脚本出现在<head>中，并且在您运行它时div 不存在。
将函数分配给onload，而不是其返回值。
window.onload=startmarquee;
您可以复制脚本并将其放在正文结束标记之前并删除window.onload=startmarquee();从而确保所有元素都已加载并可访问
就像@Quentin说的，当你引用它时，带有 id 的元素可能没有加载到 DOM 中