CSS绝对定位元素居中的几种方法

转载自-CSS居中绝对https://www.cnblogs.com/skura23/p/6530556.html

1，div宽度未知1

<body>
  <div style="position: absolute; left: 50%;">
    <div style="position: relative; left: -50%; border: dotted red 1px;">
      没有宽度<br />
      照样居中，嘿嘿嘿
    </div>
  </div>
</body>

demo：https://jsfiddle.net/skura23/0123wmsg/

2，div宽度未知2

<div class="outer">
    <div class="inner">居中<br/>蓄力中</div>
</div>

.outer {
    position: relative; /* or absolute */
    
    /* unnecessary styling properties */
    margin: 5%;
     80%;
    height: 500px;
    border: 1px solid red;
}

.inner {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    
    /* unnecessary styling properties */
    max- 50%;
    text-align: center;
    border: 1px solid blue;
}

demo： http://jsfiddle.net/skura23/6xo11zwv/210/

ps：此方法适合ie8以上的浏览器

3，div宽度已知

<body>
  <div>
    <div id="content">
      居中蓄力中
    </div>
  </div>
</body>

#content {
  position: absolute; 
  left: 0; 
  right: 0; 
  margin-left: auto; 
  margin-right: auto; 
   100px; /* 要设定宽度 */
}