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css深入理解之absolute

程序员文章站 2022-05-15 17:03:38
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一、absolute和float有相同的特性，包裹性和破坏性

1、absolute和float的相似(看下面的demo，如果图片在左上角，那么用float和absolute都一样)

  1 <!doctype html>  2 <html>  3 <head>  4 <meta charset="utf-8">  5 <meta name="viewport" content="width=device-width">  6 <title>absolute和float高尔基</title>  7 <style>  8 body {  9     background-color: #B0DEF5; 10     font-size: 14px; font-family: arial; 11     color: #444; 12 } 13 a { 14     color: #0078b6; 15     text-decoration: none; 16 } 17 a:hover { 18     text-decoration: underline; 19 } 20 em { 21     font-style: normal; 22     color: #aeaeae; 23     margin: 0 5px; 24 } 25 svg { 26     position: absolute; 27 } 28 .container { 29     width: 560px; height: -webkit-calc(100vh - 16px); height: calc(100vh - 16px); 30     margin-left: auto; margin-right: auto; 31     background-color: #fff; 32 } 33 .list { 34     padding: 20px; 35     position: relative; 36 } 37 .space { 38     padding-left: 60px; 39     line-height: 22px; 40 } 41 .space img { 42     vertical-align: text-bottom; 43 } 44 .info { 45     font-size: 12px; 46     overflow: hidden; 47     color: #808080; 48 } 49 .from { 50     float: left; 51 } 52 .from a { 53     color: #9abbc8; 54 } 55 p { 56     margin: 6px 0; 57 } 58 .operate { 59     float: right; 60 } 61 .operate img { 62     vertical-align: text-bottom; 63     margin-right: 3px; 64 } 65 .test { 66     position: relative; 67     font-size: 18px; font-family: 'microsoft yahei'; 68 } 69 .test p { 70    width: 200px; 71    margin-left: auto; margin-right: auto; 72    padding: 5px; 73    background-color: #f0f0f0;     74 } 75 .test input { 76     width: 20px; height: 20px; 77     vertical-align: -4px; 78 } 79 </style> 80 </head> 81  82 <body> 83 <p class="container"> 84     <svg xmlns="http://www.w3.org/2000/svg" width="520" height="360"> 85         <path d="M45 80C45 280,45 320,165 300" stroke-width="1" stroke="#444" fill="none"></path> 86     </svg> 87     <p class="list"> 88         <a href="#" id="avatar" class="avatar" style="float: left;"><img src="http://img.mukewang.com/54447ac70001f5cc00500050.jpg"></a> 89         <p class="space"> 90             <a href="//weibo.com/mukewang" target="_blank" title="慕课网">慕课网</a> 91             <img src="http://img.mukewang.com/54447b1a0001750000160013.png"> 92             <a href="http://huati.weibo.com/k/%E6%85%95%E8%AF%BE%E7%BD%91%E6%B4%BB%E5%8A%A8?from=501">#慕课网活动#</a>【全民晒课ing，火速赢取IT图书】无论你是慕课网的“资深粉丝”，还是刚加入的新同学，在慕课网活动帖：<a href="http://www.imooc.com/wenda/detail/30394">http://www.php.cn/</a> 写下你在慕课网所学习的任意一门课程，并附上课程的学习心得，就有机会赢得精品IT好书。<img src="http://img.mukewang.com/54447cc700010dbf00220022.gif">这事很急哒，仅有2天呦。在<a href="http://huati.weibo.com/k/%E7%A8%8B%E5%BA%8F%E5%91%98%E8%8A%82?from=501">#程序员节#</a>送给自己一份礼物吧！<img src="http://img.mukewang.com/54447af90001ab1c00010001.gif"> 93             <p><img src="http://img.mukewang.com/54447aea0001f43301200084.jpg"></p> 94             <p class="info">     95                    <span class="from"> 96                     <a href="#">9月13日 10:27</a>  97                     <em>来自</em><a href="#">微博 weibo.com</a>                       98                 </span> 99                 <span class="operate">100                     <a href="javascript:" title="赞"><img src="http://img.mukewang.com/54447c350001055b00120013.png">(4)</a><em>|</em>101                     <a href="javascript:">转发(5)</a><em>|</em>102                     <a href="javascript:">收藏</a><em>|</em>103                     <a href="javascript:">评论(2)</a>104                 </span>105             </p>106         </p>107     </p>108     <p class="test">109         <p><input type="radio" name="layout" id="float" checked><label for="float">float: left;</label></p>110         <p><input type="radio" name="layout" id="absolute"><label for="absolute">position: absolute;</label></p>111     </p>112 </p>113 <script>114 var eleAvatar = document.getElementById("avatar"),115     eleFloat = document.getElementById("float"),116     eleAbsolute = document.getElementById("absolute");117 118 // SVG路径以及相关动画119 var elePath = document.querySelector("path"), timerPath = null;    
120 var funPathMove = function(end) {121     clearTimeout(timerPath);122     var d = elePath.getAttribute("d"), arrD = d.split(" ");123     // 动画起始值124     var start = arrD.slice(-1) * 1;125     if (start == end) return;126     // 速率127     var rate = 5, current = start;128     console.log(arrD);129     var step = function() {130         if (Math.abs(end - current) < 1) {131             current = end;132         } else {133             current += (end - current) / 5;134             timerPath = setTimeout(step, 30);135         }136         // 替换最后一个值137         arrD.splice(-1, 1, current);138         // 曲线走起139         elePath.setAttribute("d", arrD.join(" "));140     };141     step();142 };143 144 if (eleAvatar && eleFloat && eleAbsolute) {145     var attrFloat = eleAvatar.style.cssFloat != undefined? "cssFloat": "styleFloat";146     eleFloat.onclick = function() {147         eleAvatar.style.position = "";148         eleAvatar.style[attrFloat] = "left";149         elePath && funPathMove(300);150     };151     eleAbsolute.onclick = function() {152         eleAvatar.style[attrFloat] = "";153         eleAvatar.style.position = "absolute";154         elePath && funPathMove(340);155     };156 }157 </script>158 </body>159 </html>

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2、破坏性

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <title>absolute的破坏性</title> 7 <style> 8 .box { 9     padding: 10px;10     background-color: #f0f0f0;    11 }12 input {13     position: absolute; top: 234px;    14     width: 160px; height: 32px;15     font-size: 100%;16 }17 </style>18 </head>19 20 <body>21 <p class="box"><img id="image" src="http://img.mukewang.com/54447b06000171a002560191.jpg" width="256" height="191"></p>22 <input id="button" type="button" value="图片absolute化">23 <script>24 var eleImg = document.getElementById("image"), eleBtn = document.getElementById("button");25 if (eleImg != null && eleBtn != null) {26     eleBtn.onclick = function() {27         if (this.absolute) {28             eleImg.style.position = "";29             this.value = "图片absolute化";30             this.absolute = false;31         } else {32             eleImg.style.position = "absolute";33             this.value = "图片去absolute";34             this.absolute = true;35         }36     };37 }38 </script>39 </body>40 </html>

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3、包裹性

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <title>absolute的包裹性</title> 7 <style> 8 .box { 9     padding: 10px;10     background-color: #f0f0f0;    11 }12 input {13     position: absolute; top: 234px;    14     width: 160px; height: 32px;15     font-size: 100%;16 }17 </style>18 </head>19 20 <body>21 <p id="box" class="box"><img src="http://img.mukewang.com/54447b06000171a002560191.jpg" width="256" height="191"></p>22 <input id="button" type="button" value="容器absolute化">23 <script>24 var eleBox = document.getElementById("box"), eleBtn = document.getElementById("button");25 if (eleBox != null && eleBtn != null) {26     eleBtn.onclick = function() {27         if (this.absolute) {28             eleBox.style.position = "";29             this.value = "容器absolute化";30             this.absolute = false;31         } else {32             eleBox.style.position = "absolute";33             this.value = "容器去absolute";34             this.absolute = true;35         }36     };37 }38 </script>39 </body>40 </html>

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二、absolute的独立性

absolute使用的时候，不一定非要和relative在一起，可以独立使用，而且它越独立，能力越大

css深入理解之absolute

三、absolute特性

1、去浮动

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>折翼天使表现特性一：去浮动</title> 6 <style> 7 input[type=button] { 8     height: 32px; 9     font-size: 100%;    10 }11 </style>12 </head>13 14 <body>15 <img src="http://img.mukewang.com/54447b06000171a002560191.jpg">16 <img src="http://img.mukewang.com/54447f4a0001eb7d01910256.jpg">17 <img src="http://img.mukewang.com/54447f550001ccb002560191.jpg">18 <p><input type="button" id="float" value="点击第2张图片应用float:left"></p>19 <p><input type="button" id="button" value="点击第2张图片应用position:absolute"></p>20 <script>21 var flbtn = document.getElementById("float"),22     button = document.getElementById("button"),23     image2 = document.getElementsByTagName("img")[1];24 if (flbtn && button && image2) {25     var value_init = button.value;26     button.onclick = function() {27         if (this.value == value_init) {28             image2.style.position = "absolute";29             this.value = "撤销";30         } else {31             image2.style.position = "";32             this.value = value_init;33         }34     };35     36     flbtn.onclick = function() {37         image2.style["cssFloat" in this.style? "cssFloat": "styleFloat"] = "left";38     };39 }40 </script>41 </body>42 </html>

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2、位置跟随

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>折翼天使表现特性二：位置跟随</title> 6 <style> 7 input[type=button] { 8     height: 32px; 9     font-size: 100%;10 }11 p { margin-left: 260px; }12 img + p { margin-top: 60px; }13 </style>14 </head>15 16 <body>17 <img src="http://img.mukewang.com/54447b06000171a002560191.jpg">18 <p><img src="http://img.mukewang.com/54447f4a0001eb7d01910256.jpg"></p>19 <img src="http://img.mukewang.com/54447f550001ccb002560191.jpg">20 <p><input type="button" id="block" value="点击第2张图片应用display:block"></p>21 <p><input type="button" id="button" value="点击第2张图片应用position:absolute变天使"></p>22 <script>23 var block = document.getElementById("block"),24     button = document.getElementById("button"),25     image2 = document.getElementsByTagName("img")[1];26 if (block && button && image2) {27     var value_init_button = button.value;28     button.onclick = function() {29         if (this.value == value_init_button) {30             image2.style.position = "absolute";31             this.value = "撤销";32         } else {33             image2.style.position = "";34             this.value = value_init_button;35         }36     };37     38     var value_init_block = block.value;39     block.onclick = function() {40         if (this.value == value_init_block) {41             image2.style.display = "block";42             this.value = "撤销";43         } else {44             image2.style.display = "";45             this.value = value_init_block;46         }    
47     };48 }49 </script>50 </body>51 </html>

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3.超越overflow

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>超越overflow</title> 6 <style> 7 body { 8     background-color: #bbb; 9 }10 .scroll {11     width: 500px; height: 300px;12     margin: 200px auto 0;13     margin-top: -webkit-calc(50vh - 150px);14     margin-top: calc(50vh - 150px);15     border: 1px solid #ccc;16     border-radius: 3px;17     box-shadow: 0 0 3px rgba(0,0,0,.35);18     background-color: #fff;19     overflow: auto;20 }21 .close {22     position: absolute;23     width: 34px; height: 34px;    24     margin: -17px 0 0 483px;25     background: url(http://www.php.cn/) no-repeat;26 }27 .close:hover {28     background-position: 0 -41px;    29 }30 img {31     display: block;32     margin: 10px;33 }34 </style>35 </head>36 37 <body>38 <p class="scroll">39     <a href="javascript:" class="close" title="关闭"></a>40     <img src="http://img.mukewang.com/54447b06000171a002560191.jpg">41     <img src="http://img.mukewang.com/54447f550001ccb002560191.jpg">42 </p>43 </body>44 </html>

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滑动滚动条的时候，关闭按钮不移动，因为设置了absolute

四、absolute实际使用

1、图片图标绝对定位覆盖

css深入理解之absolute

上面图片里面的Hot、推荐、vip都是用absolute实现的，而且没有用relative

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>图标定位二三事</title> 6 <style> 7 body { font: 14px/1.4 "Microsoft YaHei"; background-color: #EDEFF0; } 8 body, h3, h5 { margin: 0; } 9 img { border: 0 none; vertical-align: bottom; }10 .l { float: left; }.r { float: right; }11 .constr { width: 1200px; margin-left: auto; margin-right: auto; }12 .header { background-color: #2A2C2E; }13 .nav { height: 60px; }14 .nav-list { float: left; font-size: 14px; font-weight: 400; }15 .nav-a { display: inline-block; line-height: 20px; padding: 20px 35px; color: #B5BDC0; text-decoration: none; }16 .nav-a:hover { color: #fff; }17 18 .course { padding-top: 10px; }19 .course-list { float: left; width: 280px; height: 240px; margin: 5px 10px 15px; border-radius: 0 0 1px 1px; background-color: #F7FAF9; background-color: rgba(255,255,255,1); box-shadow: 0 1px 2px #c5c5c5; text-decoration: none; }20 .course-list-img { background-color: #6396F1; }21 .course-list-h { line-height: 50px; font-size: 14px; font-weight: 400; color: #363d40; text-align: center; }22 .course-list-tips { margin: 0 14px; font-size: 12px; color: #b4bbbf; overflow: hidden; }23 24 .icon-hot { position: absolute; width: 28px; height: 11px; margin: -6px 0 0 2px; background: url(http://www.php.cn/); }25 .icon-recom { position: absolute; line-height: 20px; padding: 0 5px; background-color: #f60; color: #fff; font-size: 12px; }26 .icon-vip { position: absolute; width: 36px; height: 36px; margin-left: -36px; background: url(http://www.php.cn/); text-indent: -9em; overflow: hidden; }27 </style>28 </head>29 30 <body>31 <p class="header">32     <p class="constr">33         <p class="nav">34             <h3 class="nav-list">35                 <a href="http://www.imooc.com/course/list" class="nav-a">课程</a>36             </h3>37             <h3 class="nav-list">38                 <a href="http://www.imooc.com/wenda" class="nav-a">问答</a>39             </h3>40             <h3 class="nav-list">41                 <a href="http://www.imooc.com/seek/index" class="nav-a">42                     求课<i class="icon-hot"></i>43                 </a>44             </h3>45         </p>46     </p>47 </p>48 49 <p class="main">50     <p class="constr">51         <p class="course">52             <a href="http://www.imooc.com/view/121" class="course-list">53                 <p class="course-list-img">54                     <span class="icon-recom">推荐</span>55                     <img width="280" height="160" alt="分享：CSS深入理解之float浮动" src="http://img.mukewang.com/53d74f960001ae9d06000338-300-170.jpg"><!--56                     --><i class="icon-vip">vip</i>57                 </p>58                 <h5 class="course-list-h">分享：CSS深入理解之float浮动</h5>59                 <p class="course-list-tips">60                     <span class="l">已完结</span>61                     <span class="r">3514人学习</span>62                 </p>63             </a>64         </p>65     </p>66 </p>67 </body>68 </html>

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2、下拉框定位

css深入理解之absolute

用的是无依赖绝对定位，就是只用了absolute，没有用relative

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>下拉框定位二三事</title> 6 <style> 7 body { margin: 0; font: 14px/1.4 "Microsoft YaHei"; background-color: #EDEFF0; } 8 .constr { width: 1200px; max-width: 80%; margin-left: auto; margin-right: auto; padding-bottom: 300px; overflow: hidden; } 9 .course-sidebar { width: 262px; float: left; }10 .course-sidebar > p { border: 1px solid #e6e8e9; box-shadow: 0px 1px 2px #d5d7d8; background-color: #fff; }11 .course-sidebar-type { height: 380px; }12 .course-sidebar-search { margin-top: 20px; overflow: hidden; }13 .course-search-input { width: 200px; line-height: 18px; padding: 10px; margin: 0; border: 0 none; font-size: 12px; font-family: inherit; float: left; }14 .course-sidebar-search.focus { border-color: #2ea7e0; }15 .course-search-input:focus { outline: 0 none; }16 .course-search-input::-ms-clear { display: none; }17 .course-search-btn { width: 38px; height: 38px; float: right; background: url(http://www.php.cn/); text-indent: -9em; overflow: hidden; }18 .focus .course-search-btn { background-position: 0 -38px; }19 20 .course-sidebar-result { display: none; position: absolute; width: 260px; margin: 39px 0 0 -1px; padding-left: 0; list-style-type: none; border: 1px solid #e6e8e9; background-color: #fff; box-shadow: 0px 1px 2px #d5d7d8; font-size: 12px; }21 .course-sidebar-result > li { line-height: 30px; padding-left: 12px; }22 .course-sidebar-result > li:hover { background-color: #f9f9f9; }23 .course-sidebar-result a { display: block; color: #5e5e5e; text-decoration: none; }24 .course-sidebar-result a:hover { color: #000; }25 </style>26 </head>27 28 <body>29 <p class="constr">30     <p class="course-sidebar">31         <p class="course-sidebar-type"></p>32         <p class="course-sidebar-search">33             <ul id="result" class="course-sidebar-result">34                 <li><a href="http://www.imooc.com/view/121">分享：CSS深入理解之float浮动</a></li>35                 <li><a href="http://www.imooc.com/view/118">案例：CSS圆角进化论</a></li>36                 <li><a href="http://www.imooc.com/view/93">案例：CSS Sprite雪碧图应用</a></li>37                 <li><a href="http://www.imooc.com/view/77">案例：CSS3 3D 特效</a></li>38                 <li><a href="http://www.imooc.com/view/57">案例：如何用CSS进行网页布局</a></li>39             </ul>40             <input class="course-search-input" placeholder="课程搜索">41             <a href="javascript:" class="course-search-btn">搜索</a>42         </p>43     </p>44 </p>45 <script>46 (function() {47     var input = document.getElementsByTagName("input")[0],48         result = document.getElementById("result");49         50     if (input && result) {51         input.onfocus = function() {52             this.parentNode.className = "course-sidebar-search focus";53             if (this.value != "") {54                 // show datalist55                 result.style.display = "block";56             }57         };58         input.onblur = function() {59             if (this.value == "") {60                 this.parentNode.className = "course-sidebar-search";61             }62             // hide datalist63             result.style.display = "none";64         };65         66         // IE7 that wrap a p for avoid bad effect from float67         if (!document.querySelector) {68             var p = document.createElement("p");69             input.parentNode.insertBefore(p, input);70             p.appendChild(result);71         }72         // events of datalist73         if ("oninput" in input) {74             input.addEventListener("input", function() {75                 if (this.value.trim() != "") {76                     result.style.display = "block";77                 } else {78                     result.style.display = "none";79                 }80             });81         } else {82             // IE6-IE883             input.onpropertychange = function(event) {84                 event = event || window.event;85                 if (event.propertyName == "value" && /focus/.test(this.parentNode.className)) {86                     if (this.value != "") {87                         result.style.display = "block";88                     } else {89                         result.style.display = "none";90                     }91                 }92             }93         }94     }95 96 })();97 </script>98 </body>99 </html>

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3、居中、边缘定位

css深入理解之absolute

实现图片居中和边缘定位的一种思路，可以用无限制的absolute，里面用了&nbsp;和absolute的跟随性，注意代码中的&nbsp;，这个很重要

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>居中、边缘定位二三事</title> 6 <style> 7 body { margin: 0; font: 14px/1.4 "Microsoft YaHei"; background-color: #EDEFF0; } 8 .constr { width: 1200px; max-width: 80%; margin-left: auto; margin-right: auto; } 9 .course-content { float: right; position: relative; width: 920px; min-height: 1200px; background: #fff; }10 .course-list-x { padding: 20px 10px; overflow: hidden; }11 .course-list { float: left; width: 280px; height: 240px; margin: 5px 10px 15px; border-radius: 0 0 1px 1px; background-color: #F7FAF9; background-color: rgba(255,255,255,1); box-shadow: 0 1px 2px #c5c5c5; text-decoration: none; }12 13 .goto_top_diaocha, .goto_top_app, .goto_top_feed { display: block; width: 48px; height: 48px; margin-top: 10px; background: url(http://www.php.cn/) no-repeat; }14 .goto_top_diaocha { background-position: -48px 0; }15 .goto_top_diaocha:hover { background-position: -48px -50px; }16 .goto_top_app { background-position: -96px 0; }17 .goto_top_app:hover { background-position: -96px -50px; }18 .goto_top_feed { background-position: -144px 0; }19 .goto_top_feed:hover { background-position: -144px -50px; }20 21 .course-loading-x { height: 0; margin-top: 20px; text-align: center; letter-spacing: -.25em; overflow: hidden; }22 .course-loading { position: absolute; margin-left: -26px; }23 24 .course-fixed-x { height: 0; text-align: right; overflow: hidden; }25 .course-fixed { display: inline; position: fixed; margin-left: 20px; bottom: 100px; }26 </style>27 </head>28 29 <body>30 <p class="constr">31     <p class="course-content">32         <p class="course-list-x">33             <p class="course-list"></p>34             <p class="course-list"></p>35             <p class="course-list"></p>36             <p class="course-list"></p>37             <p class="course-list"></p>38             <p class="course-list"></p>39         </p>40         <p class="course-loading-x">41             &nbsp;<img src="http://img.mukewang.com/5453077400015bba00010001.gif" class="course-loading" alt="加载中...">42         </p>43         <p class="course-fixed-x">44             &nbsp;<p class="course-fixed">45                 <a href="http://www.imooc.com/activity/diaocha" class="goto_top_diaocha"></a>46                 <a href="http://www.imooc.com/mobile/app" class="goto_top_app"></a>47                 <a href="http://www.imooc.com/user/feedback" class="goto_top_feed"></a>48             </p>49         </p>50     </p>51 </p>52 </body>53 </html>

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4、文件图片对其与定位

css深入理解之absolute

实际项目中，有的地方有星星，有的没有，想要对其文字比较麻烦，就可以用无依赖的absolute

邮箱前面的图标，以及超出框的文字，都可以用无依赖的absolute

它给页面的布局提供了一种新的思路

 1 <!doctype html> 2 <html> 3 <head> 4 <meta charset="utf-8"> 5 <title>文本图标对齐与定位二三事</title> 6 <style> 7 body { margin: 0; font: 14px/1.4 "Microsoft YaHei"; background-color: #EDEFF0; } 8 a { color: #50B6E5; } 9 .constr { width: 1200px; margin-left: auto; margin-right: auto; }10 .regist-head { height: 60px; line-height: 60px; padding-left: 30px; background-color: #be3948; color: #fff; font-size: 18px; }11 .regist-body { min-height: 400px; padding: 100px 0; background-color: #fff; }12 .regist-main { width: 600px; margin-left: auto; margin-right: auto; }13 .regist-group { margin-top: 20px; overflow: hidden; }14 .regist-label { width: 70px; padding-top: 10px; float: left; }15 .regist-cell { display: table-cell; *display: inline-block; }16 .regist-input { height: 18px; line-height: 18px; width: 260px; padding: 10px 5px; margin: 0 10px 0 0; border: 1px solid #d0d6d9; vertical-align: top; }17 .regist-code-input { width: 130px; }18 .regist-btn { display: inline-block; width: 160px; line-height: 40px; background-color: #39b94e; color: #fff; text-align: center; text-decoration: none; }19 .regist-btn:hover { background-color: #33a646; }20 .icon-warn { display: inline-block; width: 20px; height: 21px; background: url(http://www.php.cn/) no-repeat center; }21 22 .regist-star { position: absolute; margin-left: -1em; font-family: simsun; color: #f30; }23 .regist-remark { position: absolute; line-height: 21px; padding-top: 9px; color: #666; }24 .regist-warn { padding-left: 20px; color: #be3948; }25 .regist-warn > .icon-warn { position: absolute; margin-left: -20px; }26 </style>27 </head>28 29 <body>30 <p class="constr">31     <p class="regist-head">注册</p>32     <p class="regist-body">33         <p class="regist-main">34             <p class="regist-group">35                 <label class="regist-label"><span class="regist-star">*</span>登录邮箱</label>36                 <p class="regist-cell">37                     <input type="email" class="regist-input"><span class="regist-remark regist-warn">38                         <i class="icon-warn"></i>邮箱格式不准确（演示）39                     </span>40                 </p>41             </p>42             <p class="regist-group">43                 <label class="regist-label"><span class="regist-star">*</span>登录密码</label>44                 <p class="regist-cell">45                     <input type="password" class="regist-input"><span class="regist-remark">46                         请输入6-16位密码，区分大小写，不能使用空格47                     </span>48                 </p>49             </p>50             <p class="regist-group">51                 <label class="regist-label"><span class="regist-star">*</span>用户昵称</label>52                 <p class="regist-cell">53                     <input type="password" class="regist-input">54                 </p>55             </p>56             <p class="regist-group">57                 <label class="regist-label">手机号码</label>58                 <p class="regist-cell">59                     <input type="tel" class="regist-input">60                 </p>61             </p>62             <p class="regist-group">63                 <label class="regist-label"><span class="regist-star">*</span>验 证 码</label>64                 <p class="regist-cell">65                     <input class="regist-input regist-code-input"><img src="http://img.mukewang.com/545308540001678401500040.jpg">66                 </p>67             </p>68             <p class="regist-group">69                 <label class="regist-label">&nbsp;</label>70                 <p class="regist-cell">71                     <input type="checkbox" checked><label>我已阅读并同意<a href="##">慕课协议</a>。</label>72                     <p>73                         <a href="javascript:" class="regist-btn">立即注册</a>74                     </p>75                 </p>76             </p>77         </p>78     </p>79 </p>80 </body>81 </html>

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四、absolute的脱离文档流

动画尽量作用在absolute上，因为absolute是脱离文档流的，这样动画的时候就不会影响其他元素

  z-index无依赖
  1.如果只有一个绝对定位元素，自然不需要z-index,自动覆盖普通元素；
  2.如果两个绝对定位，控制DOM流的前后顺序达到需要的覆盖效果，依然无z-index；
  3.如果多个绝对定位交错，非常非常少见，z-index:1控制；
  4.如果非弹窗类的绝对定位元素z-index>2,必定z-index冗余，请优化！

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