元素垂直水平居中

html程式碼

<div class="wrap">
    <div class="inner"></div>
</div>
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1. absolute+transform實現

style程式碼

<style>
    .wrap {
      border: 1px solid palevioletred;
      height: 200px;
      width: 200px;
      position: relative;
    }
    .inner {
      border: 1px solid palevioletred;
      width: 50%;
      height: 50%;
      position: absolute;
      left: 50%;
      top: 50%;
      transform: translate(-50%,-50%);
    }
</style>
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left:50%中的百分比是相對於定位父級的寬度。
translate:50%是相對於自身的寬度。
缺點：ie9以上支援

2. absolute+margin實現

style程式碼

<style>
    .wrap {
      border: 1px solid palevioletred;
      height: 200px;
      width: 200px;
      position: relative;
    }
    .inner {
      border: 1px solid palevioletred;
      width: 50%;
      height: 50%;
      position: absolute;
      top: 50%;
      left: 50%;
      margin-left: -25%;
      margin-top: -25%;
    }
</style>
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left:50%中的百分比是相對於定位父級的寬度。
margin:50%是相對於自身的寬度。

3.absolute+margin:auto實現

  <style>
    .wrap {
      border: 1px solid palevioletred;
      height: 200px;
      width: 200px;
      position: relative;
    }
    .inner {
      border: 1px solid palevioletred;
      width: 50%;
      height: 50%;
      position: absolute;
      top: 0;
      left: 0;
      bottom: 0;
      right: 0;
      margin: auto;
    }
  </style>
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3.flex+margin:auto實現

  <style>
    .wrap {
      border: 1px solid palevioletred;
      height: 200px;
      width: 200px;
      display: flex;
    }
    .inner {
      border: 1px solid palevioletred;
      width: 50%;
      height: 50%;
      margin: auto;
    }
  </style>
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4.flex實現

  <style>
    .wrap {
      border: 1px solid palevioletred;
      height: 200px;
      width: 200px;
      display: flex;
      justify-content: center;
      align-items: center;
    }
    .inner {
      border: 1px solid palevioletred;
      width: 50%;
      height: 50%;
    }
  </style>
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