html文件：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>基本选择器</title>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
<li id="four">4</li>
<li>5</li>
<li class="green yellow">6</li>
<li class="green">7</li>
<li>8</li>
<li>9</li>
<li>10</li>
</ul>
<div class="green">111</div>
<div class="green">111</div>
<div class="green">111</div>
<div class="green">111</div>
<script src="jquery-1.12.4.js"></script>
<script>
//入口函数
$(function(){
//jquery如何设置样式
//css(name, value)
//name:样式名 value：样式值
//id选择器 $("#id")
//$("#four").css("backgroundColor", "red");
//$(".green").css("backgroundColor", "green");
//$("li").css("color", "red");
//交集 并集
//$("#four,.green").css("backgroundColor", "pink");
//$("li.green").css("backgroundColor", "red");
$(".green.yellow").css("backgroundColor", "pink");
});
</script>
</body>
</html>