js 定时器应用

<input id="button1" type="button" value="开始" >
<input id="button2" type="button" value="关闭" >
    <script>
        window.onload = function () {
            var btn1 = document.getElementById("button1");
            var btn2 = document.getElementById("button2");
           // btn1.οnclick= setInt(showInfo, 1000);
            var timer = null;
            btn1.onclick = function () {
                timer = setInterval(showInfo, 1000);
            }
            btn2.onclick= function () {
                clearInterval(timer);
            }
        };
    </script>