blocks|key|45182|text|通过使用Moment.js，您可以使用以下代码将所有内容舍入到一天的开头：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|45183|moment().startOf('day').toString();
//+->+Prints+out+"Fri+Dec+05+2014+00:00:00+GMT-0800"|code-block|syntax|javascript|45184|您可以在docs中阅读有关startOf()的更多信息。|offset|length|style|CODE|45185|entityMap|0|LINK|mutability|MUTABLE|url|http://momentjs.com/docs/#/manipulating/start-of/^0|0|0|D|9|4|4|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@$I|Z|J|10|1|11]]|A|$]]|$1|M|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

<p>Using Moment.js, you can use the following code to round everything to the beginning of the day:</p>

<pre><code>moment().startOf('day').toString();
// -&gt; Prints out "Fri Dec 05 2014 00:00:00 GMT-0800"
</code></pre>

<p>You can read more about <code>startOf()</code> in the <a href="http://momentjs.com/docs/#/manipulating/start-of/">docs</a>.</p>


blocks|key|45244|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|45245|Date.prototype.formatDate+=+function()+{
+++var+yyyy+=+this.getFullYear().toString();
+++var+mm+=+(this.getMonth()%2B1).toString();
+++var+dd++=+this.getDate().toString();
+++return+yyyy+%2B+(mm[1]?mm:"0"%2Bmm[0])+%2B+(dd[1]?dd:"0"%2Bdd[0]);
++};

var+utcSeconds+=+1417903843000,
++++d+=+new+Date(0);

d.setUTCSeconds(Math.round(+utcSeconds+/+1000.0));

var+myTime+=+(function(){
++++++++var+theTime+=+moment(d.formatDate(),+'YYYYMMDD').startOf('day').fromNow();
++++++++if(theTime.match('hours+ago')){
++++++++++++return+'Today';
++++++++}
++++++++return+theTime;
++++})();

alert(+myTime+);|code-block|syntax|javascript|45246|http://jsfiddle.net/cdn5rvck/4/|offset|length|45247|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|V|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|T|8|@]|9|@$I|U|J|V|1|W]]|A|$]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|H]]]]

<p>Try this:</p>

<pre><code>Date.prototype.formatDate = function() {
   var yyyy = this.getFullYear().toString();
   var mm = (this.getMonth()+1).toString();
   var dd  = this.getDate().toString();
   return yyyy + (mm[1]?mm:"0"+mm[0]) + (dd[1]?dd:"0"+dd[0]);
  };

var utcSeconds = 1417903843000,
    d = new Date(0);

d.setUTCSeconds(Math.round( utcSeconds / 1000.0));

var myTime = (function(){
        var theTime = moment(d.formatDate(), 'YYYYMMDD').startOf('day').fromNow();
        if(theTime.match('hours ago')){
            return 'Today';
        }
        return theTime;
    })();

alert( myTime );
</code></pre>

<p><a href="http://jsfiddle.net/cdn5rvck/4/" rel="nofollow">http://jsfiddle.net/cdn5rvck/4/</a></p>


blocks|key|4551834|text|function+roundDownDate(date)+{
++if+(typeof+date+!==+"object"+%7C%7C+!date.getUTCMilliseconds)+{
++++++throw+Error("Arg+must+be+a+Date+object.");
++}
++var+offsetMs+=+date.getTimezoneOffset()+*+60+*+1000,
++++++oneDayMs+=+24+*+60+*+60+*+1000;
++return+new+Date(Math.floor((date.getTime()+-+offsetMs)+/+oneDayMs)+*+oneDayMs+%2B+offsetMs);
};|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4551835|这应该是可行的，而且速度相当快。|unstyled|4551836|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>function roundDownDate(date) {
  if (typeof date !== "object" || !date.getUTCMilliseconds) {
      throw Error("Arg must be a Date object.");
  }
  var offsetMs = date.getTimezoneOffset() * 60 * 1000,
      oneDayMs = 24 * 60 * 60 * 1000;
  return new Date(Math.floor((date.getTime() - offsetMs) / oneDayMs) * oneDayMs + offsetMs);
};
</code></pre>

<p>This should work and is pretty fast.</p>


blocks|key|4551885|text|function+getDateOfTimeStamp(time)+{
++var+originTime+=+0;
++var+offsetOriginTime+=+originTime+%2B+new+Date().getTimezoneOffset()+*+60+*+1000;
++var+timeSinceOrigin+=+time+-+offsetOriginTime;
++var+timeModulo+=+timeSinceOrigin+%25+(24+*+60+*+60+*+1000);
++var+normalizedTime+=+time+-+timeModulo;

++console.log(new+Date(normalizedTime)+,new+Date(time));
++return+normalizedTime;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4551886|这对我的项目很有效。纯数学，不需要字符串操作，不需要外部库，所以它超级快。|unstyled|4551887|您可以尝试将上述函数复制到javascript控制台，然后执行normalizeTimeToDate(Date.now())|offset|length|style|CODE|4551888|entityMap^0|0|0|V|V|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|P|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|F|7|T|8|@]|9|@]|A|$]]]|N|$]]

<pre><code>function getDateOfTimeStamp(time) {
  var originTime = 0;
  var offsetOriginTime = originTime + new Date().getTimezoneOffset() * 60 * 1000;
  var timeSinceOrigin = time - offsetOriginTime;
  var timeModulo = timeSinceOrigin % (24 * 60 * 60 * 1000);
  var normalizedTime = time - timeModulo;

  console.log(new Date(normalizedTime) ,new Date(time));
  return normalizedTime;
}
</code></pre>

<p>This worked for my project. Pure math, no string manipulation needed, no external lib needed, so it's super fast.</p>

<p>You can try by copying the above function to javascript console and then do <code>normalizeTimeToDate(Date.now())</code></p>


blocks|key|45361|text|只需使用年、月和日期从现有日期构造一个新日期即可。添加半天以确保这是最近的日期。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|45362|​|45363|var+offset+=+new+Date(Date.now()+%2B43200000);
var+rounded+=+new+Date(offset+.getFullYear(),offset+.getMonth(),offset+.getDate());
console.log(new+Date());
console.log(rounded);|code-block|syntax|javascript|45364|45365|由于这似乎具有较小的内存使用量，因此扩展原型以将其包含在Date+"class“中也是有用的。|45366|45367|Date.prototype.round+=+function(){
++++var+dateObj+=+new+Date(%2Bthis%2B43200000);
++++return+new+Date(dateObj.getFullYear(),+dateObj.getMonth(),+dateObj.getDate());
};
console.log(new+Date().round());|45368|45369|最小化：|45370|Date.prototype.round+=+function(){var+d+=+new+Date(%2Bthis%2B43200000);return+new+Date(d.getFullYear(),+d.getMonth(),+d.getDate());};|45371|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|X|8|@]|9|@]|A|$G|H]]|$1|I|3|C|5|6|7|Y|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|Z|8|@]|9|@]|A|$]]|$1|L|3|C|5|6|7|10|8|@]|9|@]|A|$]]|$1|M|3|N|5|F|7|11|8|@]|9|@]|A|$G|H]]|$1|O|3|C|5|6|7|12|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|13|8|@]|9|@]|A|$]]|$1|R|3|S|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|T|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|U|$]]

<p>Just construct a new Date from the existing one using only the year, month, and date. Add half a day to ensure that it is the closest date.</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var offset = new Date(Date.now() +43200000);
var rounded = new Date(offset .getFullYear(),offset .getMonth(),offset .getDate());
console.log(new Date());
console.log(rounded);</code></pre>
</div>
</div>
</p>

<p>Since this seems to have a small footprint, it can also be useful to extend the prototype to include it in the Date "class".</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>Date.prototype.round = function(){
    var dateObj = new Date(+this+43200000);
    return new Date(dateObj.getFullYear(), dateObj.getMonth(), dateObj.getDate());
};
console.log(new Date().round());</code></pre>
</div>
</div>
</p>

<p>Minimized:</p>

<pre><code>Date.prototype.round = function(){var d = new Date(+this+43200000);return new Date(d.getFullYear(), d.getMonth(), d.getDate());};
</code></pre>


blocks|key|4551960|text|下面是一种简洁的方法，可以在一行中只获取日期，而不需要依赖关系：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4551961|let+d+=+new+Date().setHours(0,+0,+0,+0);|code-block|syntax|javascript|4551962|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>Here is a clean way to get just the date in one line with no dependencies:</p>

<pre><code>let d = new Date().setHours(0, 0, 0, 0);
</code></pre>


<p>I need to group a bunch of items in my web app by date created.</p>

<p>Each item has an exact timestamp, e.g. <code>1417628530199</code>. I'm using <a href="http://momentjs.com/" rel="noreferrer">Moment.js</a> and its "<a href="http://momentjs.com/docs/#/displaying/fromnow/" rel="noreferrer">time from now</a>" feature to convert these raw timestamps into nice readable dates, e.g. <code>2 Days Ago</code>. I then want to use the readable date as a header for a group of items created on the same date.</p>

<p>The problem is that the raw timestamps are too specific - two items that are created on the same date but a minute apart will each have a unique timestamp. So I get a header for <code>2 Days Ago</code> with the first item underneath, then another header for <code>2 Days Ago</code> with the second item underneath, etc.</p>

<p>What's the best way to round the raw timestamps to the nearest date, so that any items created on the same date will have the exact same timestamp and thus can be grouped together?</p>


Round a timestamp to the nearest date

我需要在我的web应用程序中按创建日期对一堆项目进行分组。每一项都有确切的时间戳，例如1417628530199。我正在使用和它的"“特性将这些原始时间戳转换成易于阅读的日期，例如2 Days Ago。然后，我想使用可读日期作为在同一日期创建的一组项目的标题。问题是原始的时间戳太具体了--两个在同一日期创建但相隔一分钟...

问将时间戳舍入到最接近的日期
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