标准日期对象的方法：
一般使用toLocaleDataString或者toLocaleString而不用toString。
小时钟案例：
<html>
<head>
<meta charset="utf-8">
<style>
#clockbox{
padding: 15px 0;
line-height: 50px;
color: aqua;
}
</style>
</head>
<body>
<div id="clockbox">
</div>
</body>
<script>
let clockbox = document.querySelector("#clockbox");
//进行补零
function addZero(val){
val = Number(val);
return val<10?'0'+val:val;
}
//转换成所需格式
function queryData(){
let time = new Date(),//获取当前日期
year = time.getFullYear(),
month = time.getMonth()+1,//0-11
day = time.getDate(),
week = time.getDay(),//0-6
hours = time.getHours(),
minutes = time.getMinutes(),
seconds = time.getSeconds();
//进行字符串拼接
let weekary = ['日','一','二','三','四','五','六'];
let result = `${year}年${addZero(month)}月${addZero(day)}日`;
result += `星期${weekary[week]} ${addZero(hours)}时${addZero(minutes)}分${addZero(seconds)}秒`;
clockbox.innerHTML = result;
}
//每隔一秒执行一次
setInterval(queryData,1000);
</script>
</html>