blocks|key|330233|text|在JavaScript中，null的含义与undefined非常不同。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|330234|JSON输出应该反映应用程序在使用JSON数据的特定上下文中使用和需要的内容。|330235|entityMap^0|D|4|L|9|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

In JavaScript, <code>null</code> means something very different than <code>undefined</code>.

Your JSON output should reflect what is used and needed by your application in the specific context of using the JSON data.

blocks|key|547047|text|如果需要区分null和undefined，你绝对应该包括它，因为它们在Javascript中有两种不同的含义。您可以将null视为属性未知或无意义，而将undefined视为属性不存在。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|547048|另一方面，如果任何人都不需要做出这样的区分，那么就去掉它吧。|547049|entityMap^0|6|4|B|9|1N|4|24|9|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|I|$]]

You should definitely include it if there is any need to distinguish between <code>null</code> and <code>undefined</code> since those have two different meanings in Javascript. You can think of <code>null</code> as meaning the property is unknown or meaningless, and <code>undefined</code> as meaning the property doesn't exist.

On the other hand, if there is no need for anyone to make that distinction then go ahead and leave it out.

blocks|key|547090|text|第二种方法将节省少量的带宽，但如果需要考虑这一点，您还可以使用索引数组，而不是使用键填充JSON。显然，["Foo+Bar","Joe+Blow"]比您现在拥有的要短得多。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|547091|在可用性方面，我不认为这有什么不同。在这两种情况下，if(json.isbn)都会跳到else。通常不需要区分null+(无值)和undefined+(无给定值)。|547092|entityMap^0|1G|M|0|Q|D|17|4|1J|4|1T|9|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|I|$]]

The second will save a small amount on bandwidth, but if that were a concern you would also use indexed arrays instead of filling the JSON with keys. Clearly, <code>["Foo Bar","Joe Blow"]</code> is much shorter than what you have now.

In terms of usability, I don't think it makes any difference. In both cases, <code>if(json.isbn)</code> will skip to the <code>else</code>. There is usually no need to distinguish between <code>null</code> (no value) and <code>undefined</code> (no given value).

blocks|key|330526|text|我喜欢总是显式地包含null，因为这意味着有意义。而省略一个属性则会留下歧义。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|330527|只要您与服务器的协议达成一致，上面的任何一个都可以工作，但如果您从服务器传递空值，我相信这将使您的API稍后更加灵活。|330528|还应该提到的是，javascript的hasOwnProperty函数给了你更多的洞察力。|330529|/*+if+true+object+DOES+contain+the+property+with+*some*+value+*/
if(+objectFromJSON.hasOwnProperty(+"propertyName"+)+)

/*+if+true+object+DOES+contain+the+property+and+it+has+been+set+to+null+*/
if(+jsonObject.propertyName+===+null+)

/*+if+true+object+either+DOES+NOT+contain+the+property
+++OR
+++object+DOES+contain+the+property+and+it+has+been+set+to+undefined+*/
if(+jsonObject.propertyName+===+undefined+)|code-block|syntax|javascript|330530|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|P|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I am a fan of always including null explicitly as that carries meaning.
While omitting a property leaves ambiguity.

As long as your protocol with the server is agreed upon any of the above can work, but if you pass nulls from the server I believe that makes your APIs more flexible later.

Should also mention that javascript's hasOwnProperty function gives you further insight.

<pre><code>/* if true object DOES contain the property with *some* value */
if( objectFromJSON.hasOwnProperty( "propertyName" ) )

/* if true object DOES contain the property and it has been set to null */
if( jsonObject.propertyName === null )

/* if true object either DOES NOT contain the property
 OR
 object DOES contain the property and it has been set to undefined */
if( jsonObject.propertyName === undefined )
</code></pre>

blocks|key|547386|text|当使用JSON作为API数据载体时，是否有null或空(未定义)值没有区别。可能，空的更好，因为我们节省了一些有效负载的大小。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|547387|当您想要手动编辑某些内容时，JSON-config文件就会有所不同。最好在那里有空值，而不是未定义的道具。通过这种方式，您将提供有关配置属性存在的提示。|547388|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|$]]

When JSON is used as API data carrier, there is no difference if there is a null or empty (undefined) value. Probably, the empty is better because we save some payload size.
The difference appears for JSON-config files when you would like to edit something by hands. It is better to have nulls there instead of undefined props. This way you will give hints about the config props existence.

I'm creating an API that returns results as JSON. Is there a current best practice for whether we should include keys in the result when the value is null? For example:

<pre class="lang-js prettyprint-override"><code>{
 "title":"Foo Bar",
 "author":"Joe Blow",
 "isbn":null
}
</code></pre>

or

<pre class="lang-js prettyprint-override"><code>{
 "title":"Foo Bar",
 "author":"Joe Blow"
}
</code></pre>

Since the second is smaller I am leaning towards this style, but I'm not sure if there is a preferred style or not. From a client perspective it seems like both styles would be functionally equivalent. Any pros or cons to each?

Should JSON include null values

服务器

JSON

我正在创建一个以JSON格式返回结果的API。当值为空时，我们是否应该在结果中包含键，是否有当前的最佳实践？例如：{    "title":"Foo Bar",    "author":"Joe Blow",    "isbn":null}或{    "title":"Foo Bar",    "author":"Jo...

问JSON是否应包含空值
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