jquery基本选择器(.class选择器)

//通过class属性值匹配元素
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
 <head>
  <title>.class选择器</title>
  <meta http-equiv="Content-Type" content="text/html;charset=UTF-8" />
  <style type="text/css">
  .class1{color:red;}
  </style>
  <script  type="text/javascript" src="jquery-1.7.1.min.js"></script>
  <script type="text/javascript">
        window.onload=function(){
            document.getElementById('btnOk').onclick=function(){
                $(' .class1 ').html('php'); //把使用.class1的元素匹配并内容替换
            };
        };
  </script>
 </head>
 <body>
  <div id="div1">div1</div>
  <hr/>
  <div class="class1">div2</div>
  <hr/>
  <p class="class1">杨</p>
  <input type="button" id='btnOk' value='确定'  />
 </body>
</html>