显示当前时间，点击按钮，显示当前系统时间

代码如下

<script>
    function tim() {
        var date = new Date();//当前系统时间
        var year = date.getFullYear();
        var month = date.getMonth();
        var de = date.getDate();
        var hours = date.getHours();
        var minutes = date.getMinutes();
        var seconds = date.getSeconds();
        var time = document.querySelector("span");
        time.innerHTML = year+'-'+month+'-'+de+'  '+hours+':'+minutes+':'+seconds;
    }
</script>