blocks|key|181439|text|首先，这是javascript，而不是JSON。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|181440|解决方案：|181441|data:+{
++++userId:+7,
++++actionId:+36
}
if(myCondition)+data["express"]+=+true;|code-block|syntax|javascript|181442|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

first of all, thats javascript, not JSON.

the solution:

<pre><code>data: {
 userId: 7,
 actionId: 36
}
if(myCondition) data["express"] = true;
</code></pre>

blocks|key|180435|text|你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|180436|var+json+=+JSON.stringify(+{
++++data:+{
++++++++userId:+7,
++++++++actionId:+36,
++++++++express:+(myCondition+?+true+:+null)
++++}
});|code-block|syntax|javascript|180437|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|$]]

You could do something like this:

<pre><code>var json = JSON.stringify( {
 data: {
 userId: 7,
 actionId: 36,
 express: (myCondition ? true : null)
 }
});
</code></pre>

blocks|key|181456|text|如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|181457|data:+{
++++userId:+7,
++++actionId:+36,
++++express:+(myCondition+?+true+:+undefined)
}|code-block|syntax|javascript|181458|当您将对象stringify为JSON时，值为JSON的属性不会被写入。|offset|length|181459|181460|编辑:从评论中看，实际上并没有涉及到JSON。OP使用的是$.ajax，所以可能使用了$.param。不幸的是，$.param确实为值为undefined的属性创建了一个条目。因此，如果没有任何补充代码行，可能就没有解决方案。|style|CODE|181461|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify^0|0|0|5|9|0|0|0|T|6|17|7|1K|7|1W|9|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Z|8|@]|9|@$I|10|J|11|1|12]]|A|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|14|8|@$I|15|J|16|N|O]|$I|17|J|18|N|O]|$I|19|J|1A|N|O]|$I|1B|J|1C|N|O]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]]]

Do it like this :

<pre><code>data: {
 userId: 7,
 actionId: 36,
 express: (myCondition ? true : undefined)
}
</code></pre>

A property whose value is <code>undefined</code> isn't written when you <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify">stringify</a> the object to JSON.

<hr>

EDIT : It appears from the comments that there is no JSON involved in fact. OP is using <code>$.ajax</code> so <code>$.param</code> is probably used. <code>$.param</code>, unfortunately, does create an entry for properties whose value is <code>undefined</code>. So there's probably no solution without any supplementary line of code.

blocks|key|183059|text|如果您使用匿名函数而不是对象文字表示法来定义对象，则可以做到这一点：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|183060|var+data+=+new+function(){
++++this.userId+=+7;
++++this.actionId+=+36;
++++myCondition+&&+(this.express+=+true);
};|code-block|syntax|javascript|183061|得到的data对象是完全相同的，除了它的constructor将是匿名函数，而不是window.Object。|offset|length|style|CODE|183062|entityMap^0|0|0|3|4|K|B|15|D|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]|$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|N|$]]

You can do it if you define your object using an anonymous function instead of object literal notation:

<pre><code>var data = new function(){
 this.userId = 7;
 this.actionId = 36;
 myCondition &amp;&amp; (this.express = true);
};
</code></pre>

The resulting <code>data</code> object is the exact same, except it's <code>constructor</code> will be the anonymous function instead of <code>window.Object</code>.

blocks|key|2792589|text|有点老了，但也有一个好的解决方案，你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2792590|data:+{
++++userId:+7,
++++actionId:+36
}

Object.assign(data,+!myCondition+&&+{+express:+yourValue+});|code-block|syntax|javascript|2792591|因此，如果您的条件为false，它将为您的express属性分配所需的值。|2792592|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

A bit old but there is a good solution as well you can do :

<pre><code>data: {
 userId: 7,
 actionId: 36
}

Object.assign(data, !myCondition &amp;&amp; { express: yourValue });
</code></pre>

Thus it will assign your express property with the value you need if your condition is false.

blocks|key|180516|text|使用spread+operator。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|180517|data:+{
++++userId:+7,
++++actionId:+36,
++++...myCondition+&&+{express:+true}
}|code-block|syntax|javascript|180518|请注意，如果您使用的是Flow，则该语法可能会生成类型检查错误。您可以更明确地、也可以不那么简洁地编写上面的代码，如下所示：|180519|data:+{
++++userId:+7,
++++actionId:+36,
++++...(myCondition+?+{express:+true}+:+{})
}|180520|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator#Spread_in_object_literals|1|https://flow.org/^0|2|F|0|0|0|B|4|1|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|K|3|L|5|F|7|15|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

Use the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator#Spread_in_object_literals" rel="noreferrer">spread operator</a>.

<pre><code>data: {
 userId: 7,
 actionId: 36,
 ...myCondition &amp;&amp; {express: true}
}
</code></pre>

Note that if you're using <a href="https://flow.org/" rel="noreferrer">Flow</a>, that syntax might generate type check errors. You can write the above more explicitly, and less succinctly, as:

<pre><code>data: {
 userId: 7,
 actionId: 36,
 ...(myCondition ? {express: true} : {})
}
</code></pre>

blocks|key|181533|text|扩展运算符现在可以修复此问题。下面是一个包含两个比较的示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|181534|注意:我将date:更改为const+date+=，这样它就是有效的可运行javascript。这也可以与data:一起使用，如果它被认为是在深层对象结构中。|offset|length|style|CODE|181535|​|181536|const+compareValue+=+13;
const+data+=++{
++++userId:+7,
++++actionId:+36,
++++...(compareValue+>+10+&&+{propertyForGreaterThan10:+'foo'}),
++++...(compareValue+<+10+&&+{propertyForLessThan10:+'bar'}),
}
console.log(data);|code-block|syntax|javascript|181537|181538|entityMap^0|0|5|5|D|C|1H|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@$D|T|E|U|F|G]|$D|V|E|W|F|G]|$D|X|E|Y|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|Z|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|10|8|@]|9|@]|A|$M|N]]|$1|O|3|I|5|6|7|11|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|Q|$]]

The spread operator now fixes this. Here is an example with two comparisons.
Note: I changed <code>date:</code> to <code>const date = </code> so that it is valid runnable javascript. This can also be used with <code>data:</code> if it is supposed to be inside of a deep object structure.
<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>const compareValue = 13;
const data = {
 userId: 7,
 actionId: 36,
 ...(compareValue &gt; 10 &amp;&amp; {propertyForGreaterThan10: 'foo'}),
 ...(compareValue &lt; 10 &amp;&amp; {propertyForLessThan10: 'bar'}),
}
console.log(data);</code></pre>
</div>
</div>

Is there some syntax for setting properties based on a condition?

<pre><code>data: {
 userId: 7,
 actionId: 36,
 express: (myCondition ? true : null) // does not work
}
</code></pre>

I want <code>express</code> to be either set to a value or not set at all (i.e., there should be no key named <code>express</code>), and without extra statements after the definition. I know I can use it as a boolean, but the receiving side is using an <code>isset()</code> check and I'm wondering if I can avoid modifying it.

<hr>

Edit: Seems there is no direct solution to the problem as stated. Here are the close suggestions:

JSON.stringify (Chris Kessel, dystroy):

<pre><code>var json = JSON.stringify( {
 data: {
 userId: 7,
 actionId: 36,
 express: (myCondition ? true : null)
 }
});
</code></pre>

An anonymous function (Paulpro):

<pre><code>var data = new function(){
 this.userId = 7;
 this.actionId = 36;
 myCondition &amp;&amp; (this.express = true);
};
</code></pre>

An extra statement (x4rf41):

<pre><code>data: {
 userId: 7,
 actionId: 36
}
if(myCondition) data["express"] = true;
</code></pre>

Eval (a former colleague of mine):

<pre><code>eval("data = {userId: 7, actionId: 36 " + (myCondition ? ", express: true}" : "}"))
</code></pre>

Conditional definition (don't really know how to label this one):

<pre><code>data = (
 (myCondition &amp;&amp; { userId: 7, actionId: 36, express: true }) ||
 (!myCondition &amp;&amp; { userId: 7, actionId: 36 })
);
</code></pre>

Conditionally set an object property

JSON

是否有一些基于条件设置属性的语法？data: {    userId: 7,    actionId: 36,    express: (myCondition ? true : null) // does not work}我希望express要么被设置为一个值，要么根本不被设置(即，不应该有名为express的键)...

问有条件地设置对象属性
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