为什么我用$("#arron:nth-child(1)").css("color","blue");就不能改变颜色
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<title></title>
<style>
a {
font-size: 30px;
font-weight: 900;
}
div {
width: 200px;
height: 100px;
background-color: yellow;
color: red;
}
</style>
<script src="http://libs.baidu.com/jquery/1.9.1/jquery.js"></script>
</head>
<body>
<h2>get方法</h2>
<div id="aaron">
<a>1</a>
<a>2</a>
<a>3</a>
<a>4</a>
<a>5</a>
</div>
<select id="animation">
<option value="1">get正数索引参数</option>
<option value="2">get负数索引参数</option>
</select>
<input id="exec" type="button" value="点击执行">
<script type="text/javascript">
$("#exec").click(function() {
$("#arron:nth-child(1)").css("color","blue");
var v = $("#animation").val();
var $aaron = $("#aaron a");
//通过get找到第二个a元素，并修改蓝色字体
if (v == "1") {
} else if (v == "2") {
//通过get找到最后一个a元素，并修改字体颜色
$aaron.get(-1).style.color = "#8A2BE2"
}
});
</script>
</body>
</html>
