最简单的getElementById问题。 [英] Simplest getElementById question ever.
问题描述
为什么这不起作用？
<！DOCTYPE HTML PUBLIC" - // W3C // DTD HTML 4.01 Transitional // EN"
http：//www.w3.org/TR/html4/loose.dtd">
< html>
< head>
< meta http-equiv =" Content-Type" content =" text / html;
charset = iso-8859-1">
< script language =" javascript">
alert（document.getElementById（''pst''））;
< / script>
< / head>
< body>
< div id =" subject">
< form action =""方法= QUOT;获得"大于1。你想
< div id =" pst">
< a href ="＃">写一个支持意见< / a> ;或者< a href ="＃">写一个
不同意见< / a>，或者< a href ="＃">写一般评论< / a>
< / div>
< p id =" subject_list">& nbsp;< / p>
< / form>
< / div>
< / body>
< / html>
它杀了我。有什么明显的东西我不见了吗？谢谢。
Why isn''t this working?
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<script language="javascript">
alert(document.getElementById(''pst''));
</script>
</head>
<body>
<div id="subjects">
<form action="" method="get">1. Would you like to
<div id="pst">
<a href="#">write a supporting opinion</a>, or <a href="#">write a
differing opinion</a>, or <a href="#">write a general comment</a>
</div>
<p id="subject_list"> </p>
</form>
</div>
</body>
</html>
It''s killing me. Is there something obvious I''m missing? Thanks.
推荐答案
文件必须先加载才能引用document.getElementById;
将它包装在一个函数中并调用它onload：
< script language =" javascript">
函数saywhat（）{
alert（document.getElementById（''pst''））;
}
onload = sayWhat;
< ; / script>
The document has to load before you can reference document.getElementById;
wrap it in a function and call it onload:
<script language="javascript">
function saywhat(){
alert(document.getElementById(''pst''));
}
onload=sayWhat;
</script>
Rich Hephner写道：
Rich Hephner wrote:
为什么不是'这有用吗？
<！DOCTYPE HTML PUBLIC" - // W3C // DTD HTML 4.01 Transitional // EN"
" http：//www.w3.org /TR/html4/loose.dtd">
< html>
< head>
< meta http-equiv =" Content-Type" content =" text / html;
charset = iso-8859-1">
< script language =" javascript">
alert（document.getElementById（''pst ''））;
< / script>
Why isn''t this working?
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<script language="javascript">
alert(document.getElementById(''pst''));
</script>
浏览器解析文档并在解析时执行脚本块
it所以在此时调用document.getElementById（''pst''）它
返回null，因为找不到具有该id属性值的元素。所以如果你看到一个带有null的警告对话框，那么
的例子会按预期工作。
也许你想使用
window.onload = function（ evt）{
alert（document.getElementById（''pst''））;
};
-
Martin Honnen
http：// JavaScript。 FAQTs.com/
Rich Hephner在16 mei 2005上写了comp.lang.javascript ：
Rich Hephner wrote on 16 mei 2005 in comp.lang.javascript:
为什么这不起作用？
<！DOCTYPE HTML PUBLIC" - // W3C // DTD HTML 4.01 Transitional // EN"
" http://www.w3.org/TR/html4/loose.dtd">
< html>
< head>
< meta http-equiv ="内容型" content =" text / html;
charset = iso-8859-1">
< script language =" javascript">
alert（document.getElementById（''pst ''））;
< / script>
< / head>
< body>
< div id =" subject">
< form action =""方法= QUOT;获得"大于1。你想
< div id =" pst">
< a href ="＃">写一个支持意见< / a>，或者< a href = "＃">写一个
不同意见< / a>，或< a href ="＃">写一般性评论< / a>
< / div>
< p id =" subject_list">& nbsp;< / p>
< / form>
< / div>
< / body> ;
< / html>
它杀了我。有什么明显的东西我不见了吗？谢谢。
Why isn''t this working?
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1">
<script language="javascript">
alert(document.getElementById(''pst''));
</script>
</head>
<body>
<div id="subjects">
<form action="" method="get">1. Would you like to
<div id="pst">
<a href="#">write a supporting opinion</a>, or <a href="#">write a
differing opinion</a>, or <a href="#">write a general comment</a>
</div>
<p id="subject_list"> </p>
</form>
</div>
</body>
</html>
It''s killing me. Is there something obvious I''m missing? Thanks.
1执行警报时元素尚不存在。
2你可能不喜欢我想要显示元素，但是该元素的一些可写属性
，如tagNeme，一些样式元素或innerHTML。
IE将返回[object]但是其他浏览器可以有其他想法。
-
Evertjan。
荷兰。
（在我的电子邮件地址中用点替换所有十字架）
1 the element does not yet exist at the time your alert is executed.
2 you probably don''t want to show the element, but some writable property
of that element, like the tagNeme, some style element or the innerHTML.
IE would return [object] but other browsers could have other ideas.
--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)
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