console 命令行工具 X clear

console

var curtime = new Date();
var endtime = new Date('2017,6,6');
var lefttime = Math.ceil((endtime.getTime() - curtime.getTime()) / (24 * 60 * 60 * 1000));

document.getElementById('timeShow').innerHTML = '高考倒计时' + lefttime + '天'

<span id="timeShow"> </span>