CSS规则visibility:hidden和display:none都会导致元素不可见。这些是同义词吗?
当前回答
有一件事值得补充,尽管它没有被问到,是有第三个选项,使对象完全透明。考虑:
1 <a href="http://example.com" style="display: none;"> < / >链接。< br / > <a href="http://example.com" style="可见性:隐藏;"> < / >链接。< br / > <a href="http://example.com" style="不透明度:0;"> < / >链接。
(请务必点击上面的“运行代码片段”按钮查看结果。)
1和2之间的区别已经指出了(即2仍然占据空间)。但是,2和3之间有区别:在情况3中,鼠标停留在链接上时仍然会切换到手,用户仍然可以单击链接,Javascript事件仍然会在链接上触发。这通常不是你想要的行为(但有时可能是?)
另一个区别是,如果你选择文本,然后复制/粘贴为纯文本,你会得到以下结果:
1st link.
2nd link.
3rd unseen link.
在情况3中,文本被复制了。也许这对于某种类型的水印是有用的,或者如果你想隐藏一个版权声明,如果一个粗心的用户复制/粘贴你的内容会显示出来?
其他回答
显示:没有;既不会显示元素,也不会在页面上为元素分配空间,而可见性:隐藏;不会在页面上显示元素,但会在页面上分配空间。 在这两种情况下,我们都可以访问DOM中的元素。 为了更好地理解它,请查看以下代码: 显示:无vs可见性:隐藏
这里有很多详细的答案,但我认为我应该加上这一点来解决可访问性问题,因为其中有影响。
显示:没有;可见性:隐藏;可能不是所有屏幕阅读器软件都能读取。记住视力受损的用户将会经历什么。
这个问题还问了同义词。indent: -9999 px;是另一个大致相等的。文本缩进的重要区别在于它通常由屏幕阅读器读取。这可能是一个有点糟糕的体验,因为用户仍然可以点击链接。
对于可访问性,我现在看到的是一种样式的组合,在对屏幕阅读器可见的情况下隐藏元素。
{
clip: rect(1px, 1px, 1px, 1px);
clip-path: inset(50%);
height: 1px;
width: 1px;
margin: -1px;
overflow: hidden;
padding: 0;
position: absolute;
}
一个很好的做法是创建一个“跳转到内容”链接到内容主体的锚。视力受损的用户可能不想在每个页面上都听完整的导航树。使链接在视觉上隐藏。用户只需点击标签就可以访问链接。
有关可访问性和隐藏内容的更多信息,请参见:
https://webaim.org/techniques/css/invisiblecontent/ https://webaim.org/techniques/skipnav/
display: none;
它将不会出现在页面上,也不会占用任何空间。
visibility: hidden;
它隐藏了一个元素,但它仍然会占用与之前相同的空间。元素将被隐藏,但仍然会影响布局。
可见性:隐藏保留空间,而显示:无不保留空间。
无示例:https://www.w3schools.com/css/tryit.asp?filename=trycss_display_none
示例:https://www.w3schools.com/cssref/tryit.asp?filename=trycss_visibility
另一个区别是可见性:hidden在非常非常老的浏览器中有效,而display:none则不行:
https://www.w3schools.com/cssref/pr_class_visibility.asp
https://www.w3schools.com/cssref/pr_class_display.asp
总结所有其他答案:
visibility | display |
---|---|
element with visibility: hidden, is hidden for all practical purposes (mouse pointers, keyboard focus, screenreaders), but still occupies space in the rendered markup | element with display:none, is hidden for all practical purposes (mouse pointers, keyboard focus, screenreaders), and DOES NOT occupy space in the rendered markup |
css transitions can be applied for visibility changes | css transitions can not be applied on display changes |
you can make a parent visibility:hidden but a child with visibility: visible would still be shown | when parent is display:none, children can't override and make themselves visible |
part of the DOM tree (so you can still target it with DOM queries) | part of the DOM tree (so you can still target it with DOM queries) |
part of the render tree | NOT part of the render tree |
any reflow / layout in the parent element or child elements, would possibly trigger a reflow in these elements as well, as they are part of the render tree. | any reflow / layout in the parent element, would not impact these elements, as these are not part of the render tree |
toggling between visibility: hidden and visible, would possibly not trigger a reflow / layout. (According to this comment it does: What is the difference between visibility:hidden and display:none? and possibly according to this as well https://developers.google.com/speed/docs/insights/browser-reflow) | toggling between display:none to display: (something else), would lead to a layout /reflow as this element would now become part of the render tree |
you can measure the element through DOM methods | you can not measure the element or its descendants using DOM methods |
If you have a huge number of elements using visibility: none on the page, the browser might hang while rendering, as all these elements require layout, even though they are not shown | If you have a huge number of elements using display:none, they wouldn't impact the rendering as they are not part of the render tree |
资源:
https://developers.google.com/speed/docs/insights/browser-reflow http://www.stubbornella.org/content/2009/03/27/reflows-repaints-css-performance-making-your-javascript-slow/ visibility:hidden和display:none
其他信息:
还有一些浏览器支持特性,但它们似乎适用于非常老的浏览器,在其他答案中也有,所以我在这里没有讨论它们。 还有其他一些隐藏元素的方法,比如不透明度,或者屏幕外的绝对定位。所有这些方法在一些或其他的回答中都有涉及,并且都有一些缺点。 根据这条评论(可见性:hidden和display:none之间的性能差异),如果你有很多元素使用display:none并且你将其更改为display:(其他),它将导致单个回流,而如果你有多个可见性:hidden元素并且你将它们变为可见,它将导致每个元素的回流。(我不太明白)