从上级元素开始匹配后代的某些子元素:find()
<div class='father'>
<div class="son-1"></div>
<div class="son-2"></div>
<div class="son-3"></div>
<div class="son-4">
<div class="son-4-1"></div>
</div>
</div>
<javascript>
$('.father').find('.son-4-1');
</javascript>
从元素本身开始,逐级向上级元素匹配,并返回最先匹配的元素:closest()
<javascript>
$('.son-4-1').find('.father');
</javascript>