1 $("ul li:eq(3)")

1 $("ul li:lt(2)")

1 $("ul li:gt(2)")

1 $("[name^=‘user‘]")

1 $("[name$=‘ge‘]")

1 $("[name*=‘na‘]")

1 $("[name*=‘name‘][id *= ‘username‘]")

 1 $("input[reg]").each(function(){
 2         var val = $(this).val();
 3         var tip = $(this).attr("tip");
 4         var reg = $(this).attr("reg");
 5         var regexp = new RegExp(reg);
 6         if(!regexp.test(val)){
 7             alert(tip)
 8         }
 9     })
10 
11 
12 <input   type = "text"  name = "username" id = "username" reg = "^\w{1,12}$" tip = "Name Input format does not conform to the requirements"/>
13 <input   type = "password" name = "password" id = "password" reg = "^\w{1,12}$" tip = "PassWord Input format does not conform to the requirements"/>
14 
15 <input   type = "text" name = "email" id = "email" reg = "^\w*\@\w*\.\w*$" tip = "Email Input format does not conform to the requirements"/>