JS获取日期的方法实例【昨天,今天,明天,前n天,后n天的日期】

2019-11-19 15:16:25

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本文实例讲述了JS获取日期的方法。分享给大家供大家参考，具体如下：

原理很简单，一天的时间的毫秒数是1000*60*60*24，

前n天的日期就是现在日期换成毫秒-n*1000*60*60*24。

再把这个值换成日期即可（通过setTime方法）

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>www.VeVB.COm 日期计算</title> <meta name="Generator" content="EditPlus"> <meta name="Author" content=""> <meta name="Keywords" content=""> <meta name="Description" content=""> </head> <body> <select id="num" name="num" style="width:150px" onchange="ff()">        <option value="-1">昨天</option>        <option value="0">今天</option>        <option value="1">明天</option> </select><br> <textarea id="ar" rows="3" cols="20"> haha</textarea><br/><input type="text" value="" name="bday" id="bday"/>天之前<input type="button" onclick="bday()" value="计算"><br/><input type="text" value="" name="aday" id="aday"/>天之后<input type="button" onclick="aday()" value="计算"><br/> </body> <script> ff();function ff(){ var obj=document.getElementById("num"); var v1=obj.options[obj.selectedIndex].text; var v2=obj.options[obj.selectedIndex].value; var tvv=giveDateStr(getTargetday(v2)); document.getElementById('ar').innerText=tvv;}function isInteger(obj) { var r = /^/+?[1-9][0-9]*$/;　　//正整数  return r.test(obj); }function bday(){ var bef=document.getElementById("bday").value; if(isInteger(bef)){   var bvv=giveDateStr(getTargetday(-bef));   document.getElementById('ar').innerText=bvv; }else{   alert("请输入正整数！");   document.getElementById("bday").value='';   document.getElementById("bday").focus(); } }function aday(){ var atf=document.getElementById("aday").value; if(isInteger(atf)){   var avv=giveDateStr(getTargetday(atf));   document.getElementById('ar').innerText=avv; }else{   alert("请输入正整数！");   document.getElementById("aday").value='';   document.getElementById("aday").focus(); }}function getTargetday(num){  var number=null;  if(num==null||num==0){   number=0;  }else{    number=num;  }  var  today=new  Date();  var  targetday_milliseconds=today.getTime()+1000*60*60*24*number;  var  targetday=new  Date();  targetday.setTime(targetday_milliseconds); //注意，这行是关键代码  return targetday;}function giveDateStr(dd){  var riqiyue=dd.getMonth()+1;  var riqihao=dd.getDate();  var riqixingqi=null;  if(dd.getDay()=='0'){   xingqi="星期日";  }else if(dd.getDay()=='1'){   xingqi='星期一';  }else if(dd.getDay()=='2'){   xingqi='星期二';  }else if(dd.getDay()=='3'){   xingqi='星期三';  }else if(dd.getDay()=='4'){   xingqi='星期四';  }else if(dd.getDay()=='5'){   xingqi='星期五';  }else if(dd.getDay()=='6'){   xingqi='星期六';  }  var riqi=riqiyue+"月"+riqihao+"日"+"("+xingqi+")";  return riqi;}</script></html>

运行效果如下：