使用display:none时隐藏DOM元素无法获取实际宽高的解决方法
<h3>案例说明</h3><p>当DOM元素被添加上display:none;的样式时，这个元素和它的子元素无法获取到实际的宽高。<br />如图，我设置了一个父元素和一个子元素，并且通过一个按钮切换父元素是否带有display:none;。</p>
<p><img alt="" src="https://img.jbzj.com/file_images/article/202207/202207280846071.png" /><img alt="" src="https://img.jbzj.com/file_images/article/202207/202207280846072.png" /></p>
<p>然后每次点击按钮后，在控制台输出两个元素的高度。</p>
<p><img alt="" src="https://img.jbzj.com/file_images/article/202207/202207280846073.png" /></p>
<p>可以看到，当元素正常显示时，获取宽高正常。而当元素添加上`display:none;`之后，获取到的值变为0.</p>
<h3>解决方法</h3>
<p>使用jquery的actual方法可以很方便的获取到元素的真实宽高。<br /><script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.actual/1.0.19/jquery.actual.min.js"></script><br />语法格式<br />//获取带有.hidden类的元素的实际高度<br />$('.hidden').actual('height');<br />使用actual方法后获取宽高正常，无论元素有没有被设置display:none;。(下图中两次输出，一次是带有display:none;的，一次是没有的，均能获取到实际高度)</p>
<p><img alt="" src="https://img.jbzj.com/file_images/article/202207/202207280846074.png" /></p>
<p>原理：设置display:none;的元素没有物理尺寸，而同样能提供隐形效果的visibility则有物理尺寸，但是不能直接用visibility:hidden;代替display:none;，因为设置visibility之后的元素还是会占用页面空间的。正确的解决方法是要获取宽度或者高度时，首先将display:none;更换成display:block;,然后设置visibility让其隐形，从而获取实际宽高。</p>
<p>这里需要注意的是，当元素设置为块级元素时，可能会因为其大小使得周围的元素被推动，因此我们在获取某个元素的实际宽高时，除了设置display和visibility，还要设置position:absolute;,在获取到宽高值之后取消掉。</p>
<p>这个实现方法其实就是jquery的actual方法的内容：</p>
<p>源地址<a href="https://github.com/dreamerslab/jquery.actual" target="_blank">jquery.actual:Get the actual width/height of invisible DOM elements with jQuery</a>.</p>
<p>如果打不开github也可以看下面的代码(jquery.actual.js的代码内容)</p>
<div class="jb51code"><pre class="brush:js;">/*! Copyright 2012, Ben Lin (http://dreamerslab.com/)
* Licensed under the MIT License (LICENSE.txt).
*
* Version: 1.0.19
*
* Requires: jQuery >= 1.2.3
*/
;( function ( factory ) {
if ( typeof define === 'function' && define.amd ) {
// AMD. Register module depending on jQuery using requirejs define.
define( ['jquery'], factory );
} else {
// No AMD.
factory( jQuery );
}
}( function ( $ ){
$.fn.addBack = $.fn.addBack || $.fn.andSelf;
$.fn.extend({
actual : function ( method, options ){
// check if the jQuery method exist
if( !this[ method ]){
throw '$.actual => The jQuery method "' + method + '" you called does not exist';
}
var defaults = {
absolute : false,
clone : false,
includeMargin : false,
display : 'block'
};
var configs = $.extend( defaults, options );
var $target = this.eq( 0 );
var fix, restore;
if( configs.clone === true ){
fix = function (){
var style = 'position: absolute !important; top: -1000 !important; ';
// this is useful with css3pie
$target = $target.
clone().
attr( 'style', style ).
appendTo( 'body' );
};
restore = function (){
// remove DOM element after getting the width
$target.remove();
};
}else{
var tmp = [];
var style = '';
var $hidden;
fix = function (){
// get all hidden parents
$hidden = $target.parents().addBack().filter( ':hidden' );
style += 'visibility: hidden !important; display: ' + configs.display + ' !important; ';
if( configs.absolute === true ) style += 'position: absolute !important; ';
// save the origin style props
// set the hidden el css to be got the actual value later
$hidden.each( function (){
// Save original style. If no style was set, attr() returns undefined
var $this = $( this );
var thisStyle = $this.attr( 'style' );
tmp.push( thisStyle );
// Retain as much of the original style as possible, if there is one
$this.attr( 'style', thisStyle ? thisStyle + ';' + style : style );
});
};
restore = function (){
// restore origin style values
$hidden.each( function ( i ){
var $this = $( this );
var _tmp= tmp[ i ];
if( _tmp === undefined ){
$this.removeAttr( 'style' );
}else{
$this.attr( 'style', _tmp );
}
});
};
}
fix();
// get the actual value with user specific methed
// it can be 'width', 'height', 'outerWidth', 'innerWidth'... etc
// configs.includeMargin only works for 'outerWidth' and 'outerHeight'
var actual = /(outer)/.test( method ) ?
$target[ method ]( configs.includeMargin ) :
$target[ method ]();
restore();
// IMPORTANT, this plugin only return the value of the first element
return actual;
}
});
}));</pre></div>
<h3>actual方法的参数</h3>
<div class="jb51code"><pre class="brush:js;">Example Code:(来源于jquery.actual github项目说明)
// get hidden element actual width
$( '.hidden' ).actual( 'width' );
// get hidden element actual innerWidth
$( '.hidden' ).actual( 'innerWidth' );
// get hidden element actual outerWidth
$( '.hidden' ).actual( 'outerWidth' );
// get hidden element actual outerWidth and set the `includeMargin` argument
$( '.hidden' ).actual( 'outerWidth', { includeMargin : true });
// get hidden element actual height
$( '.hidden' ).actual( 'height' );
// get hidden element actual innerHeight
$( '.hidden' ).actual( 'innerHeight' );
// get hidden element actual outerHeight
$( '.hidden' ).actual( 'outerHeight' );
// get hidden element actual outerHeight and set the `includeMargin` argument
$( '.hidden' ).actual( 'outerHeight', { includeMargin : true });
// if the page jumps or blinks, pass a attribute '{ absolute : true }'
// be very careful, you might get a wrong result depends on how you makrup your html and css
$( '.hidden' ).actual( 'height', { absolute : true });
// if you use css3pie with a float element
// for example a rounded corner navigation menu you can also try to pass a attribute '{ clone : true }'
// please see demo/css3pie in action
$( '.hidden' ).actual( 'width', { clone : true });
// if it is not a block element. By default { display: 'block' }.
// for example a inline element
$( '.hidden' ).actual( 'width', { display: 'inline-block' });</pre></div>
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