如何判断jQuery节点是否位于其父节点的开头？

Question

Given the following HTML:

<p><img id="one" alt="at beginning, return true" />Some Text</p>
<p>Some <img id="two" alt="in middle, return false" />Text</p>
<p>Some Text<img id="three" alt="at end, return false" /></p>

How would I be able to tell that $("img#one") is at the beginning of its parent node?

Ideally what I'm trying to do is this:

$("p>img").each(function () {
    var $this = $(this);
    var $parent = $this.parent();
    if ("$this is at the beginning of $parent.html()") {
        $parent.before($this);
    } else {
        $parent.after($this);
    }
});

Edit: with sebasgo's help , here's the final code and result:

$("p>img").each(function () {
    var $this = $(this);
    var $parent = $this.parent();
    if (this == this.parentNode.firstChild) {
        $parent.before($this);
    } else {
        $parent.after($this);
    }
});

<img id="one" alt="at beginning, return true" />
<p>Some Text</p>
<p>Some Text</p>
<img id="two" alt="in middle, return false" />
<p>Some Text</p>
<img id="three" alt="at end, return false" />

Answer 1

Use

var elem = $("img#one").get(0)
if (elem.parentNode.firstChild == elem)
{ .... }

Hope this works better.

Answer 2

The following code will tell you if the node in question is the 'first-child' or not so should work for you. I've just been battling with a similar problem and this worked for me.

if($(this).prev().length)
{
    // Not first-child
} else {
    // is first-child
}

Answer 3

试试这个条件：

($parent.contents().eq(0).attr("id") === $this.attr("id"))

Answer 4

From similar question on SO.

How to match first child of an element only if it's not preceeded by a text node?

$("p>img").each(function () {
    var prev = this.previousSibling;
    var isThisTheFirstNode = $(this).parent().html().toUpperCase().indexOf('<IMG>') == 0;

    var method = isThisTheFirstNode ? 'before' : 'after';
    $(this).parent[method].before(this);
});