jquery按钮倒计时

<!DOCTYPE html>
<html>
<head>
    <title>发送验证码</title>
</head>
<body>
    手机号：<input type="text" name="mobile" value="" id="mobile">
    验证码：<input type="text" name="mobile" value="">
    
    <input type="button" name="submit" value="验证码" id="sendCode">
</body>
</html>
<script src="http://cdn.static.runoob.com/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript">
    $(function(){
        $(‘#sendCode‘).click(function(){
            var count = 60; // 发送频率/秒
            var countdown1 = setInterval(function(){
                    $(‘#sendCode‘).attr(‘disabled‘,true).css({‘color‘:‘#b5adad‘});
                    $(‘#sendCode‘).val(‘验证码‘+count+‘s‘);
                    if(count == 0){
                        $(‘#sendCode‘).val(‘验证码‘).removeAttr(‘disabled‘).css({‘color‘:‘#27d6df‘});
                        clearInterval(countdown1);
                    }
                    count--;
            },1000);
        });
    });    
</script>