jQuery

append

<p>
  <span class="s1">s1</span>
</p>
<script>
$("p").append('<span class="s2">s2</span>');
</script>

结果是这样的:

<p>
  <span class="s1">s1</span>
  <span class="s2">s2</span>
</p>

after

<p>
  <span class="s1">s1</span>
</p>
<script>
$("p").after('<span class="s2">s2</span>');
</script>

结果是这样的:

<p>
  <span class="s1">s1</span>
</p>
<span class="s2">s2</span>

总结：

append/prepend 是在选择元素内部嵌入。

after/before 是在元素外面追加。