jquery匹配某个祖辈元素或后代元素

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>