blocks|key|3065522|text|这是因为时间串不是往返的。如果你尝试这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3065523|var+currentTime+=+new+Date();
var+currentTimeInMill+=+Date.parse(currentTime);
var+currentTime2+=+new+Date(currentTimeInMill);

console.log(currentTime.getTime());

console.log(currentTime2.getTime());

console.log(currentTime+==+currentTime2);
//+false|code-block|syntax|javascript|3065524|你会发现时代不同了。currentTime2以3个零结尾，而currentTime有其他东西。这是一个以毫秒为单位的分钟差，日期字符串显然不包括这一点。|offset|length|style|CODE|3065525|entityMap^0|0|0|A|C|U|B|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

It's because time strings aren't round-trip. If you try this:

<pre><code>var currentTime = new Date();
var currentTimeInMill = Date.parse(currentTime);
var currentTime2 = new Date(currentTimeInMill);

console.log(currentTime.getTime());

console.log(currentTime2.getTime());

console.log(currentTime == currentTime2);
// false
</code></pre>

You'll see that the times are different. <code>currentTime2</code> ends in 3 zeroes and <code>currentTime</code> has something else. It's a minute difference, in the milliseconds, which date strings obviously don't include.

blocks|key|5135646|text|在JavaScript中，除非两个“对象”引用完全相同的object，否则您永远不会使用它们来使它们相等。Javascript相等性先检查它们是否引用相同的对象，然后再检查是否有相似的值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|5135647|简而言之，在比较对象时，==与===是相同的|CODE|5135648|你的支票应该是：|5135649|currentTime.getTime()+==+currentTime2.getTime();
//+or
%2BcurrentTime+==+%2BcurrentTime2;+//+cast+both+to+numbers+and+compare+the+numbers|code-block|syntax|javascript|5135650|entityMap^0|N|B|0|C|2|F|3|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|H]|$9|X|A|Y|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|Z|8|@]|D|@]|E|$]]|$1|K|3|L|5|M|7|10|8|@]|D|@]|E|$N|O]]|$1|P|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|Q|$]]

You won't ever get two "Objects" in JavaScript to be equal using <code>==</code> unless they reference the exact same object. Javascript equality checks to see if they reference the same object before it checks to see if any values are similar.

Put simply, when comparing objects <code>==</code> is identical to <code>===</code>

Your check should be:

<pre><code>currentTime.getTime() == currentTime2.getTime();
// or
+currentTime == +currentTime2; // cast both to numbers and compare the numbers
</code></pre>

blocks|key|1449710|text|正如minitech指出的那样，因为从Date对象的toString方法中去掉了毫秒，所以为了绝对确保currentTime的数值等于currentTime2的数值，您需要设置currentTime2的毫秒|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1449711|currentTime2.setMilliseconds(currentTime+%25+1000);|code-block|syntax|javascript|1449712|然后，就像cwolves指出的那样，你可以比较每个Date的getTime输出。|1449713|var+currentTime+=+new+Date();
var+currentTimeInMill+=+Date.parse(currentTime);
var+currentTime2+=+new+Date(currentTimeInMill);
currentTime2.setMilliseconds(currentTime+%25+1000);

//+debug+in+firefox
console.log(currentTime);
//+Date+{Thu+Jul+07+2011+09:56:19+GMT%2B1000+(AUS+Eastern+Standard+Time)}

console.log(currentTime2);
//+Date+{Thu+Jul+07+2011+09:56:19+GMT%2B1000+(AUS+Eastern+Standard+Time)}

console.log(currentTime.getTime()+==+currentTime2.getTime());|1449714|entityMap^0|Q|8|1F|B|1V|C|2G|C|0|0|P|4|U|7|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|P|$]]

Because, as minitech points out, milliseconds are stripped from the Date object's <code>toString</code> method, in order to be absolutely sure that the numeric value of <code>currentTime</code> equals that of <code>currentTime2</code>, you'll need to set the milliseconds of <code>currentTime2</code>:

<pre><code>currentTime2.setMilliseconds(currentTime % 1000);
</code></pre>

Then, as cwolves points out, you can compare each <code>Date</code>'s <code>getTime</code> output. So when complete, it would look something like this:

<pre><code>var currentTime = new Date();
var currentTimeInMill = Date.parse(currentTime);
var currentTime2 = new Date(currentTimeInMill);
currentTime2.setMilliseconds(currentTime % 1000);

// debug in firefox
console.log(currentTime);
// Date {Thu Jul 07 2011 09:56:19 GMT+1000 (AUS Eastern Standard Time)}

console.log(currentTime2);
// Date {Thu Jul 07 2011 09:56:19 GMT+1000 (AUS Eastern Standard Time)}

console.log(currentTime.getTime() == currentTime2.getTime());
</code></pre>

blocks|key|5135747|text|currentTime-currentTime2=0是测试两个日期引用相同时间戳的一种快速方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5135748|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

currentTime-currentTime2===0 is a quick way to test thet two dates refer to the same timestamp.

Hello all javascript guru,

I've came across this javascript code that struggled me abit to understand why it didn't work as expected. So thought i post it here seeking for your help.

Basically the code is to convert a Date to milliseconds format and that milliseconds value then be converted back to Date object again but when comparing, they are NOT equal?

<pre><code>var currentTime = new Date();
var currentTimeInMill = Date.parse(currentTime);
var currentTime2 = new Date(currentTimeInMill);

// debug in firefox
console.log(currentTime);
// Date {Thu Jul 07 2011 09:56:19 GMT+1000 (AUS Eastern Standard Time)}

console.log(currentTime2);
// Date {Thu Jul 07 2011 09:56:19 GMT+1000 (AUS Eastern Standard Time)}

console.log(currentTime == currentTime2);
// false
</code></pre>

My question is why that 2 values currentTime and currentTime2 are not equal even their values "look" the same in Firefox console.log?

Datetime in javascript, is it a bug?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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大家好，javascript专家，我遇到了这段javascript代码，它让我有点费力地理解为什么它不能像预期的那样工作。所以我想我把它贴在这里寻求你的帮助。基本上，代码是将日期转换为毫秒格式，然后将毫秒值再次转换回日期对象，但当进行比较时，它们是否相等？var currentTime = new Date();var...

问javascript中的Datetime，它是一个bug吗？
EN

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问javascript中的Datetime，它是一个bug吗？EN