一。 在html的checkbox里，选中的话会有属性checked="checked"。
如果用一个checkbox被选中，alert这个checkbox的属性"checked"的值alert($"#xxx".attr("checked"))，会打印出"true"，而不是"checked"！
如果没被选中，打印出的是"undefined"。觉得很奇怪是吗？继续看下去～
不要尝试去做这样的判断：if($"#xxx".attr("checked")=="true") //这样是错误的
因为这么做是错的，jQuery的API手册上写，attr(name)的返回值是object。所以，应该是 if($("#xxx").attr("checked")==true)。
判断这个值 $("input[name='weibo_count']").attr("checked"); 这样也行
<html xmlns= " http://www.w3.org/1999/xhtml "> <head runat= " server "> <SCRIPT LANGUAGE= " JavaScript "> <!-- $( " document ").ready(function(){ $( " #btn1 ").click(function(){ $( " [name='checkbox'] ").attr( " checked ", ' true '); // 全选 }) $( " #btn2 ").click(function(){ $( " [name='checkbox'] ").removeAttr( " checked "); // 取消全选 }) $( " #btn3 ").click(function(){ $( " [name='checkbox']:even ").attr( " checked ", ' true '); // 选中所有奇数 }) $( " #btn4 ").click(function(){ $( " [name='checkbox'] ").each(function(){ if($( this).attr( " checked ")) { $( this).removeAttr( " checked "); } else { $( this).attr( " checked ", ' true '); } }) }) $( " #btn5 ").click(function(){ var checks = ""; $( " input[name='checkbox[]'] ").each(function(){ if($( this).attr( " checked ") == true){ checks += $( this).val() + " | "; // 动态拼取选中的checkbox的值，用“|”符号分隔 } }) }) // --> </SCRIPT> </HEAD> <BODY> <form name= " form1 " method= " post " action= ""> <input type= " button " id= " btn1 " value= " 全选 "> <input type= " button " id= " btn2 " value= " 取消全选 "> <input type= " button " id= " btn3 " value= " 选中所有奇数 "> <input type= " button " id= " btn4 " value= " 反选 "> <input type= " button " id= " btn5 " value= " 获得选中的所有值 "> <br> <input type= " checkbox " name= " checkbox[] " value= " checkbox1 "> checkbox1 <input type= " checkbox " name= " checkbox[] " value= " checkbox2 "> checkbox2 <input type= " checkbox " name= " checkbox[] " value= " checkbox3 "> checkbox3 <input type= " checkbox " name= " checkbox[] " value= " checkbox4 "> checkbox4 </form> </body> </html>