Detailed explanation of four solutions to obtain the first li positioning of jq ul

If we just get the first li in a ul, then we can write like this:

$("ul li:first");
$("ul li"). eq(0);
$("ul li").first();
$("ul li").slice(0,1);//The first parameter of slice represents the start of selection Position, the second parameter is the ending position

<ul>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
</ul>
<ul>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
</ul>
<ul>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
</ul>
<ul>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
<li>安哲</li>
</ul>

I have probably written four solutions

<script type="text/javascript">
//方案一
$(function(){
var list=$("ul");
for (var i = 0; i < list.length; i++) {
$("ul:eq("+i+") li:first").css("background","red");
 
}
});
//方案二
/*$(function(){
$("ul").each(function(){
$(this).children().first().css("background","red"); 
});
});*/
//方案三
/*$(function(){
$("ul li:nth-child(1)").css("background","red");
});*/
//方案四
/*$(function(){
$("ul li:first-child").css("background","red");
});*/
</script>

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