blocks|key|1327748|text|当值为0时没有区别。如果是1和1em，是的，是有区别的，但无论单位是多少，0都是0。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1327749|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|$]]

There's no difference when the value is 0. If it were 1 and 1em, yes, there's a difference, but 0 is 0, no matter the unit.

blocks|key|1543077|text|这就像说0个香蕉和0个苹果不一样。因此，在某种程度上，他是正确的，但零等于零，所以无论哪种方式，你最终都会挨饿！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543078|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|$]]

It's like saying that 0 bananas is not the same as 0 apples. So in a way, he's correct, but zero is zero, so either way you'll end up hungry!

blocks|key|1543151|text|我想知道老师是否试图强调，不是0和0em不是同一个值，而是CSS中的默认单位可能不是em+(我相信规范要求非零值附加单位，但通常假设px)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543152|在具体的例子中，它们显然是相等的。|1543153|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

I wonder if the teacher is trying to highlight, not so much that 0 and 0em are not the same value but perhaps, that the default unit in CSS may not be em (I believe the spec demands that non-zero values have units attached but often assume px).

On the specific example obviously they are equal.

blocks|key|1327775|text|零等于零等于零。不管单位是否不同。以像素为单位的派生值始终是相同的:零。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1327776|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|$]]

Zero is zero is zero. Regardless of whether the units are different. The derived value in pixels is always same: zero.

blocks|key|1543209|text|看起来，你的老师是个笨蛋。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543210|但也许表象是有欺骗性的:你应该问问你的老师它们是什么意思。|1543211|我不得不问，你为什么不问你的老师他们第一次说的时候是什么意思？无论单位是多少，零都是零。|1543212|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Your teacher, it appears, is an idiot.

But maybe appearances are deceptive: you should ask your teacher what they meant.

I have to ask, why didn't you ask your teacher what they meant when they first said it? Zero is zero, no matter what the units.

blocks|key|1543388|text|带或不带关联大小单位(em、px等)的'0‘之间肯定有区别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543389|虽然在大多数情况下，CSS将没有单位大小的'0‘解释为该属性的默认零单位，但情况并不总是如此(例如，font-+size+)，当遇到没有包含该单位的参数时，一些验证器会反对在其规范中需要单位大小的属性。|1543390|不同之处在于，没有指定单位的'0‘可能会被解释为需要单位大小的属性中的表达式错误。你可能没有注意到区别，因为表达式将被简单地视为“糟糕的语法”，解释器将跳过它；就像它通常对CSS中的任何糟糕的语法所做的那样。因此，如果您指定'0‘作为单位大小，默认值为'0em’或'0%25‘等，则该属性的结果将保持为'0’。但是，如果您打算更改级联中的先前值，则会注意到这一点。'0em‘表示，’将先验值更改为'0em'，但零可能只表示‘忽略此规则’，并保留先前的规则有效。这可能根本不是你想要的裸体'0‘。|1543391|这是一个客户端进程，您无法控制特定浏览器现在或将来如何处理“0”和默认解释。|1543392|因此，除了告诉任何人阅读你的代码的人，你肯定希望有一个'0‘大小的元素，以及什么类型的单元是合适的，它实际上可能会影响结果。最好始终使用带有零的单位名称。如果你真的很挑剔(就像我一样)或者设计vls系统和代码(就像我一样)，你可能还希望把前导零(0.xx...)任何小于0的值。这可以让以后的读者知道你的片段是故意的，而不仅仅是一个打字错误。|1543393|至于那些抱怨“额外打字”的人--我建议你去上一堂打字课。在面试设计师或程序员的工作时，我做的第一件事就是给他们做一次打字测试。没有什么比优秀的打字员更省钱、更少出错的了！|1543394|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|P|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Q|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|R|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|S|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|M|$]]

There certainly is a difference between a '0' with or without an associated sizing unit (em, px, etc.).

While CSS, in most cases, interprets '0' without a unit size as a default zero-unit for that attribute, it is not always the case (font-size, for example) and some validators will object to properties which require unit sizes in their specification when they encounter a parameter without that unit included.

The difference is that '0', without a unit designation may be interpreted as an expression error in properties where unit size is required. You may not notice the difference since the expression will simply be regarded as 'bad syntax' and the interpreter will skip it; as it normally does with any bad syntax in CSS. So if you specified the '0' as a unit size and the default is '0em' or '0%' etc. then the result will remain '0' for that attribute. However, you will notice it if you intended to change a prior value in the cascade. a '0em' says, 'change the prior value to '0em', but a zero may simply say, 'disregard this rule' and leave the prior rule in effect. This may not be at all what you intended with your naked '0'.

This is a client-side process and you have no control how a particular browser, now or in the future, may handle '0' and default interpreting. 

So, besides telling whomever reads your code that you definitely intended to have a '0' sized element, and what type of unit is appropriate, it may actually effect the result. Better to always use the unit designation with your zeros. If you're really fussy (as I am) or design vls systems and code (as I have), you may also wish to put a leading zero (0.xx...) in any values less than 0. This permits later readers to know that your fraction was deliberate and not simply a typo. 

As for those who complain about 'extra typing' - I suggest you go take a typing class. One of the first things I do when interviewing designers or coders for a job is give them a typing test. There's nothing like a good typist to save money and produce fewer errors!

blocks|key|1543324|text|你的老师很固执，因为他或她不愿意承认错误。‘all+:+0’将所有可能的单位设置为零，无论是继承的还是其他的。0绝对是零。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543325|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|$]]

your teacher is being stubborn in that he or she is unwilling to admit to being wrong. 'whatever: 0' sets all possible units, inherited or otherwise, to zero. 0 is most definitely zero.

blocks|key|1543270|text|0和0em是相同的，但是x和xem中除0以外的任何值都不相同。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543271|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|$]]

0 and 0em are the same, but any value other than 0 for x and xem are not the same.

blocks|key|1543541|text|谷歌自己的“计算”风格的Chrome浏览器包括零值的单位，这符合我个人的偏好，只包括它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1543542|​|1543543|📷|atomic|offset|length|1543544|1543545|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/ddbc21d8595c68e7c19701cd6046f86c.png|imageAlt^0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@$G|V|H|W|1|X]]|A|$]]|$1|I|3|C|5|6|7|Y|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|Q|R|-4]]]]

Google's own Chrome browser in the 'Computed' style includes units with zero values which aligns with my personal preference to just include it. 

<img src="https://i.stack.imgur.com/jLRGV.png" alt="Include Units With Zero Values">

Is there any difference between 

<pre><code>margin: 0;
</code></pre>

and 

<pre><code>margin: 0em;
</code></pre>

I didn't notice anything, but my teacher keeps telling me that it's not the same.

CSS difference between 0 and 0em

解释器

两者之间有什么区别吗？margin: 0;和margin: 0em;我没有注意到任何东西，但我的老师一直告诉我这不一样。

问0和0em之间的CSS差异
EN

回答 9

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问0和0em之间的CSS差异EN

回答 9

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问0和0em之间的CSS差异
EN