前言
display、visibility、opacity三个属性隐藏元素之间的异同点一直是前端面试面试的常考题。
属性 |
值 |
是否在页面上显示 |
注册点击事件是否有效 |
是否存在于可访问性树中 |
display |
none |
否 |
否 |
否 |
visibility |
hidden |
否 |
否 |
是 |
opacity |
0 |
否 |
是 |
是 |
除了display、visibility、opacity三个属性可以隐藏元素之外,是否还存在其它属性可以隐藏元素呢?它们之间又存在什么必然的联系呢?这就是我们今天要讨论的问题。
注:由于篇幅有限,本文并未提及一些像filter:alpha(opacity=0); zoom:0;之类的兼容属性。
第一种:移除出可访问性树
display : none
display属性可以设置元素的内部和外部显示类型。将display设置为none会将元素从可访问性树中移除。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>display : none</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- display : none;
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
-
第二种:隐藏元素
visibility: hidden
将visibility设置为hidden会使元素不可见,但此时元素仍然位于可访问性树中(display: none时元素被移出可访问性树 ),注册点击事件无效。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>visibility: hidden</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- visibility: hidden;
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
第三种:透明
opacity: 0
opacity(不透明度),取值范围0(完全透明) ~ 1(完全不透明),将opacity设置为0会使元素完全透明,此时元素不可见(因为它是透明的),仍然位于可访问性树中,注册点击事件有效。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>opacity: 0</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- opacity: 0;
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
transparent
将元素的background-color、color和border-color设置为transparent(透明),此时元素不可见(因为它是透明的),仍然位于可访问性树中,注册点击事件有效。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>transparent</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- color: transparent;
- background-color: transparent;
- border-color: transparent;
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
-
rgba(0,0,0,0)
从技术上说,transparent是 rgba(0,0,0,0) 的简写,将元素的background-color、color和border-color设置为rgba(0,0,0,0)(透明),此时元素不可见(因为它是透明的),仍然位于可访问性树中,注册点击事件有效。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>rgba(0,0,0,0)</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- color: rgba(0,0,0,0);
- background-color: rgba(0,0,0,0);
- border-color: rgba(0,0,0,0);
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
-
rgba只需要第四个参数为0即可达到隐藏元素的效果。
hsla(0,0%,0%,0)
hsla使用元素隐藏的机制与rgba一致,都是由第四个参数Alpha所控制的,将元素的background-color、color和border-color设置为hsla(0,0%,0%,0),此时元素不可见(因为它是透明的),仍然位于可访问性树中,注册点击事件有效。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>hsla(0,0%,0%,0)</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- color: hsla(0,0%,0%,0);
- background-color: hsla(0,0%,0%,0);
- border-color: hsla(0,0%,0%,0);
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
-
hsla和rgba一致,只需要第四个参数为0即可达到隐藏元素的效果。
filter: opacity(0%)
filter(滤镜) opacity(0% ~ 100%)转化图像的透明程度,值范围于0%(完全透明) ~ 100%(完全不透明)之间。将元素的filter设置为opacity(0%),此时元素不可见(因为它是透明的),仍然位于可访问性树中,注册点击事件有效。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>filter: opacity(0%)</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- filter: opacity(0%);
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
第四种:缩放
transform: scale(0, 0)
将transform设置为scale(0, 0)会使元素在x轴和y轴上都缩放到0像素,此元素会显示,也会占用位置,但是因为已经缩放到0%,元素和内容占用像素比为0*0,所以看不到此元素及其内容,也无法点击。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>transform: scale(0, 0)</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- transform: scale(0,0);
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
-
width: 0;height: 0;overflow: hidden
将width和height都设置为0,使元素占用像素比为0*0,但此时会出现两种情况:
当元素的display属性为inline时,元素内容会将元素宽高拉开;
当元素的display属性为block或inline-block时,元素宽高为0,但元素内容依旧正常显示,此时再加上overflow:hidden;即可裁剪掉元素外的元素内容。
这个方法跟transform: scale(0,0)的不同点在于:transform: scale(0,0)是将元素与内容都进行缩放,而此方法是将元素缩放到0px,再裁剪掉元素外的元素内容。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>width: 0;height: 0;overflow: hidden</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- width:0;
- height:0;
- overflow: hidden;
- border-width: 0;/* user agent stylesheet中border-width: 2px; */
- padding: 0;/* user agent stylesheet中padding: 1px 6px; */
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
第五种:旋转
transform: rotateX(90deg)
将元素沿着X轴顺时针旋转90度达到隐藏元素的效果。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>transform: rotateX(90deg)</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- transform: rotateX(90deg);
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
transform: rotateY(90deg)
将元素沿着Y轴顺时针旋转90度达到隐藏元素的效果。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>transform: rotateY(90deg)</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- transform: rotateY(90deg);
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
-
第六种:脱离屏幕显示位置
脱离屏幕显示位置同样可以使元素不可见,但是达到这种效果的css样式太多了,这里只举例一种情况说明。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>脱离屏幕显示位置</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- position: fixed;
- top: -100px;
- left: -100px;
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div>
- <button id="bt">按钮</button>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
第七种:遮盖
使用元素遮盖也可以使元素不可见,因为达到这种效果的css样式也很多,故这里只举例一种情况说明。
代码:
- <!DOCTYPE html>
- <html>
- <head>
- <meta name="charset" content="utf-8"/>
- <title>遮盖</title>
- <style type="text/css">
- div {
- background-color: red;
- width: 100px;
- height: 100px;
- line-height: 100px;
- text-align: center;
- margin-top: 24px;
- }
- button {
- background-color: black;
- color: white;
- }
- #bt {
- z-index: -1;
- position: absolute;
- top: 50%;
- left: 50%;
- transform: translate(-50%,-50%);
- }
- #cover {
- z-index: 1;
- position: absolute;
- top: 0;
- left: 0;
- margin: 0;
- }
- </style>
- </head>
- <body>
- <div>
- <button id="normal">按钮</button>
- </div>
- <div style="position: relative;line-height: normal;">
- <button id="bt">按钮</button>
- <div id="cover"></div>
- </div>
-
- <script type="text/javascript">
- let normal = document.getElementById('normal');
- let bt = document.getElementById('bt');
- normal.addEventListener('click',function(){
- alert('click normal');
- })
- bt.addEventListener('click',function(){
- alert('click bt');
- })
- </script>
- </body>
- </html>
参考
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