手机短信验证发送后增加倒计时

<button class="btn blue" onclick="dr_ajax_url('/index.php?s=member&c=api&m=login_code&id='+$('#dr_phone').val()+'&code='+$('#dr_code').val())" type="button">获取手机验证码</button>

改为

<button id="sms_code" onclick="dr_ajax_sms('/index.php?s=member&c=api&m=login_code&id='+$('#dr_phone').val()+'&code='+$('#dr_code').val())" type="button">获取手机验证码</button>

<script>
var countdown = 60;
function setCountdown() {
    if (countdown == 0) {
        $('#sms_code').prop('disabled', false);
        $('#sms_code').text('获取验证码');
        countdown = 60;
    } else {
        $('#sms_code').prop('disabled', true);
        $('#sms_code').text(countdown + '秒');
        countdown--;
        setTimeout(setCountdown, 1000);
    }
}


// ajax操作
function dr_ajax_sms(url) {
    var index = layer.load(2, {
        shade: [0.3,'#fff'], //0.1透明度的白色背景
        time: 100000000
    });
    $.ajax({
        type: "GET",
        url: url,
        dataType: "json",
        success: function (json) {
            layer.close(index);
            if (json.code == 0) {
                $('.fc-code img').click();
                if (json.data.field) {
                    $('#dr_row_'+json.data.field).addClass('has-error');
                    $('#dr_'+json.data.field).focus();
                }
            }
            // 在成功回调函数中
            if (json.code == 1) {
                setCountdown();
            }
            dr_cmf_tips(json.code, json.msg, json.data.time);
            if (json.data.url) {
                setTimeout("window.location.href = '"+json.data.url+"'", 2000);
            }
        },
        error: function(HttpRequest, ajaxOptions, thrownError) {
            dr_ajax_alert_error(HttpRequest, this, thrownError);
        }
    });
}
</script>