清除div下面的所有标签的方法

<div id="slides">
<div id="content-main" name="content-main">
<div id="a">
<img src="img/example-slide-1.jpg" alt="1">
</div>
</div>
<div id="content-main" name="content-main">
<div id="b">
<img src="img/example-slide-2.jpg" alt="1">
</div>
</div>

</div>
<input id="p" type="button" value="add" onclick="add1();"/>
<input id="p" type="button" value="add33" onclick="clear();"/>