获取div元素的宽度
HTML：
<a id="postanad" href="postad.php">Make a Post</a>
CSS：
#header #postanad {
position: absolute;
top: 50px;
left: 250px ;
background: #000 url(postad.gif) repeat-x 0% 100%;
font: bold 19px Tahoma, 'trebuchet MS', Sans-serif;
padding: 5px;
}
如何确定 div 元素所采用的像素/em 大小，以便使背景图像 postad.gif 具有相同的宽度？
需要明确的是，我不想动态确定宽度，而只是想知道它占用了多少空间，以便我可以在 PS 中绘制背景图像。
HTML:
<a id="postanad" href="postad.php">Make a Post</a>
CSS:
#header #postanad {
position: absolute;
top: 50px;
left: 250px ;
background: #000 url(postad.gif) repeat-x 0% 100%;
font: bold 19px Tahoma, 'trebuchet MS', Sans-serif;
padding: 5px;
}
How do I determine the size in pixels/ems that the div element is taking so that I can make the background image postad.gif to be of the same width?
Just to be clear I don't want to determine the width dynamically , but just want to know how much space it is taking so that I can draw a background image in PS.
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如果您熟悉 jQuery，则可以使用
$("#postanad").width()。If you're comfortable with jQuery, you can just use
$("#postanad").width().如果有人只想使用简单的 javascript 使用来获取 div 的宽度：
有关更多可能性，请查看 此处。
If somebody wants just to get the width of a div with simple javascript use:
for more possibilitys have a look here.
CSS 不是一种“编程语言”。您无法真正做出决策、收集数据或操作该语言未设计的任何功能。如果你想做到这一点，javascript 是你最好的选择。
您到底希望背景发生什么？如果我们了解您的需求，我们也许能够帮助您获得纯 CSS 解决方案。
CSS isn't a 'programming language'. You can't really make decisions, gather data, or manipulate anything the language wasn't designed to do. If you want to do that, javascript is your best choice.
What exactly do you want to have happen with the background? We might be able to help you get a CSS only solution if we know your requirements.
jQuery 的方式，就像 @orthod0ks 所说的那样，是使用 width() 函数。
CSS 方式是声明
width和height或者，另一种 CSS 方式是：
您还可以在 div 上放置背景（如
background： red;），截图，粘贴到PS中看看有多大。最后，Firefox 有一个名为（MeasureIt）的插件。它对于以像素为单位确定事物的大小非常有用。因此，如果这两种解决方案都不适合您，您应该考虑一下。
祝你好运！
The jQuery way, like @orthod0ks said would be to use the width() function.
The CSS way would be to declare a
widthandheightOR, another CSS way would be to:
You can also put a background on the div (like
background: red;), take a screenshot, and paste into PS to see how big it is.Lastly, Firefox has a plugin called (MeasureIt). It is rather useful for determining sizes of things in terms of pixels. So you should look into that if both solutions are not viable for you.
Good luck!
有问题的 div 是否被动态重绘？因为如果没有的话，最简单的就是在#header #postanad 样式中设置高度和宽度。
Is the div in question being redrawn dynamically? Because if not, the easiest thing is to set the height and width in the #header #postanad style.