把所有匹配的元素插入到另一个、指定的元素元素集合的前面。

实际上，使用这个方法是颠倒了常规的$(A).before(B)的操作，即不是把B插入到A前面，而是把A插入到B前面。

返回值:jQuery

参数:

• expr (String): 用于匹配元素的jQuery表达式

示例:

与 $("#foo").before("p")相同

$("p").insertBefore("#foo"); 

HTML 代码:

<div id="foo">Hello</div><p>I would   like to say: </p>

结果:

<p>I would like to say: </p><div   id="foo">Hello</div>

insertBefore( content )

Insert all of the matched elements before another, specified, set of elements. This operation is, essentially, the reverse of doing a regular $(A).before(B), in that instead of inserting B before A, you're inserting A before B.

Return value: jQuery
Parameters:

• content (<Content>): Content to insert the selected element before.

Example:

Same as $("#foo").before("p")

 $("p").insertBefore("#foo");  

 <div id="foo">Hello</div><p>I would like to say: </p>  

 <p>I would like to say: </p><div id="foo">Hello</div>