总结--谈谈CSS几种垂直居中方式

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
</head>
<body>
  <div class="parent">
    <div class="child">
      一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字
    </div>
  </div>
</body>
</html>

.parent{
  height: 600px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  width: 300px;
  position: absolute;
  top: 50%;
  left: 50%;
  margin-left: -150px;
  height: 100px;
  margin-top: -50px;
}

1.margin-top: -50%

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
</head>
<body>
  <div class="parent">
    <div class="child">
      一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字
    </div>
  </div>
</body>
</html>

.parent{
  height: 600px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%,-50%);
}

transform: -50%

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
</head>
<body>
  <div class="parent">
    <div class="child">
      一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字
    </div>
  </div>
</body>
</html>

.parent{
  height: 600px;
  border: 1px solid red;
  position: relative;
}
.child{
  border: 1px solid green;
  position: absolute;
  width: 300px;
  height: 200px;
  margin: auto;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}

absolute margin auto

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
</head>
<body>
  <div class="parent">
    <div class="child">
      一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字一串文字
    </div>
    
  </div>
</body>
</html>

.parent{
  height: 600px;
  border: 3px solid red;
  
  display: flex;
  justify-content: center;
  align-items: center;
}
.child{
  border: 3px solid green;
  width: 300px;
}

Flex