指定查询范围
<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title></title> <script src="Scripts/jquery-1.8.2.min.js"></script> <script type ="text/javascript"> $(function () { $("#btn1").click(function () { //获取页面第一个表单 var form = $("form:first"); //指定选择器的查询上下文为form //如果没有为选择器指定上下文(只传一个参数)jq会到dom树里面查找 //如果加了上下文(传递了两个参数),那么jq就到第二个参数里查找 var checkedBox = $("input[name=chkl]:checked", form); //到指定的上下文里查找 alert(checkedBox.length); }); }); </script> </head> <body> <form action="" method ="post"> 用户名: <input type ="text" /> 密码: <input type ="password" /> <input type ="checkbox" name="chkl" /> <input type ="checkbox" name="chkl" /> <input type ="checkbox" name="chkl" /> </form> <input type ="button" id="btn1" value="点击"/> </body> </html>