發送驗證碼

輸入手機號，發送驗證碼 60s倒計時

   //驗證碼 倒計時
   var countdown=60;  
   function settime(item) {  
       if (countdown == 0) {  
           item.removeAttr("disabled");  
           item.val("獲取驗證碼");  
           countdown = 60;  
           return false;  
       } else {  
           item.attr("disabled", true);  
           item.val("重新發送(" + countdown + ")");  
           countdown--;  
       }  
       setTimeout(function() {  
           settime(item);  
       },1000);  
   } 

<input value="獲取驗證碼" readonly />