JavaScript解决生日倒计时的问题

 <div id="box">
 
        <label for="">请输入您的出生月份：</label> <input type="text">
        <label for="">请输入您的出生日期：</label> <input type="text">
        <button>确定</button>
        <label for="">距离您的生日还有：</label> <input type="text">
 
    </div>
    <script>
        var btn = document.querySelector('button');
        console.log(btn);
        btn.onclick = function () {
 
            var time1 = new Date();
            var year = time1.getFullYear();
            console.log(year);
            var ins = document.querySelectorAll('input');
            console.log(ins);
            var m2 = ins[0].value;
            var d2 = ins[1].value;
            console.log(m2, d2);
            var time2 = new Date(`${year}/${m2}/${d2} 12:00:00`);
            console.log(time2);
            var time3 = time2.getTime() - time1.getTime();
            console.log(time3);
            if (time3 < 0) {
                year = year + 1;
                console.log(year);
                var time2 = new Date(`${year}/${m2}/${d2} 12:00:00`);
                var time3 = time2.getTime() - time1.getTime();
            }
            console.log(time3);
 
            var days = Math.floor(time3 / (1000 * 60 * 60 * 24));
            console.log(days);
            ins[2].value = days;
        }
    </script>