html - 边距增加父级的高度

Question

您好，为什么子级的边距底部不增加父级的高度:

<div class="my-container">
<div class="margin">
    Hello World
</div>
<div class="margin">
    Hello World
</div>

.my-container {
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
box-sizing: border-box;
width: 300px;
background-color: #3873fe;
margin: auto;
}

.my-container .margin {
    width: 100px;
    margin: 0 auto 50px;
    background-color: #00ff82;
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}

但是如果为父级添加边框，父级的高度将会增加:

.my-container {
    border:1px solid;
}

所以我想了解为什么会出现这种差异？

Answer 1

您需要将 overflow: auto; 添加到父 div。

.my-container {
  overflow: auto;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  width: 300px;
  background-color: #3873fe;
  margin: auto;
}

.my-container .margin {
  width: 100px;
  margin: 0 auto 50px;
  background-color: #00ff82;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}

<div class="my-container">
  <div class="margin">
    Hello World
  </div>
  <div class="margin">
    Hello World
  </div>
</div>