有趣的css—隐藏元素的7种思路

css隐藏元素的7种思路

前言

displayvisibilityopacity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 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
visibility hidden
opacity 0

除了displayvisibilityopacity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

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-colorcolorborder-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,transparentrgba(0,0,0,0) 的简写,将元素的background-colorcolorborder-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)

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

widthheight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blockinline-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>

结尾

本人才疏学浅,出现错误之处,还望指出。

参考

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