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Obtain implementation code for element width and height in various scenarios_javascript skills

WBOYOriginal: 2016-05-16 18:02:221170browse

Scenario 1, the element style attribute is set to width/height

Copy code The code is as follows:

< ;div style="width:100px;">test

As above, use el.style.width. If width is not set in the style attribute, it will not be obtained using el.style.width, as follows

Copy code The code is as follows :

test

The empty string pops up in all browsers. Even if the style is embedded in the css of the page, it still cannot be obtained, as follows

Copy the code The code is as follows:

test

At this time getComputedStyle or currentStyle will come in handy.
Scenario 2, the element sets width/height by introducing a style sheet
There are two ways to introduce a style sheet, one is to use the link tag to introduce a separate css file, the other is to use the style tag directly in the html page. The second method of testing is used here. As follows

Copy the code The code is as follows:

test

100px pops up in all browsers. Note that the width and height of the element defined in the style sheet can be obtained through getComputedStyle and currentStyle.
If the width and height of the element are not set in the style attribute or in the style sheet, can it still be obtained using getComputedStyle or currentStyle? The answer is that getComputedStyle can, but currentStyle cannot. As follows

Copy the code The code is as follows:

test 
 <script> <br>function getStyle(el, name) { <br>if(window.getComputedStyle) { <br>return window.getComputedStyle(el, null); <br>}else{ <br>return el. currentStyle; <br>} <br>} <br>var div = document.getElementsByTagName('div')[0]; <br>alert(getStyle(div, 'width')); <br></script&gt ; <br>
</div> <br>div neither sets the style attribute nor introduces a style sheet. The width and height (browser default) can be obtained in Firefox/IE9/Safari/Chrome/Opera, but not in IE6/7/8, and auto is returned. <br>Note that the getStyle method here uses getComputedStyle first, and IE9 already supports this method. Therefore, the width and height can be obtained in IE9. However, IE6/7/8 does not support it and can only be obtained using currentStyle. <br>Scenario 3: The element neither sets the style attribute nor introduces a style sheet <br><div class="codetitle">
<span><a style="CURSOR: pointer" data="84427" class="copybut" id="copybut84427" onclick="doCopy('code84427')"><u>Copy the code </u></a></span> The code is as follows: </div>
<div class="codebody" id="code84427"> <br><div>test<div> <br><script> <br>function getStyle(el,name) { <br>if(window.getComputedStyle) { <br>return window.getComputedStyle(el, null)[name]; <br>}else{ <br>return el.currentStyle[name]; <br>} <br>} <br>function getWH(el, name) { <br>var val = name === "width" ? el.offsetWidth : el.offsetHeight, <br>which = name === "width" ? ['Left', 'Right'] : ['Top', 'Bottom']; <br>// display is none <br>if(val === 0) { <br>return 0; <br>} <br>for(var i = 0, a; a = which[i  ];) { <br>val -= parseFloat( getStyle(el, "border"   a   "Width") ) || 0; <br>val -= parseFloat( getStyle(el, "padding"   a) ) || 0; <br>} <br>return val   'px'; <br>} <br>var div = document.getElementsByTagName('div')[0]; <br>alert(getWH(div, 'width')); <br></script> 


思路很简单：获取元素的offsetWidth/offsetHeight，减去元素的padding和border。
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