javascript 有条件地设置对象属性
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Conditionally set an object property
提问by mcmlxxxvi
Is there some syntax for setting properties based on a condition?
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
}
I want expressto be either set to a value or not set at all (i.e., there should be no key named express), and without extra statements after the definition. I know I can use it as a boolean, but the receiving side is using an isset()check and I'm wondering if I can avoid modifying it.
我想express被设置为一个值或根本不设置（即，不应该有名为 的键express），并且在定义之后没有额外的语句。我知道我可以将它用作布尔值，但是接收方正在使用isset()支票，我想知道是否可以避免修改它。
Edit: Seems there is no direct solution to the problem as stated. Here are the close suggestions:
编辑：似乎没有直接解决上述问题的方法。以下是接近的建议：
JSON.stringify(Chris Kessel, dystroy):
JSON.stringify（Chris Kessel，dystroy）：
var json = JSON.stringify( {
data: {
userId: 7,
actionId: 36,
express: (myCondition ? true : null)
}
});
An anonymous function(Paulpro):
匿名函数（Paulpro）：
var data = new function(){
this.userId = 7;
this.actionId = 36;
myCondition && (this.express = true);
};
An extra statement(x4rf41):
额外的语句(x4rf41)：
data: {
userId: 7,
actionId: 36
}
if(myCondition) data["express"] = true;
Eval(a former colleague of mine):
Eval（我的前同事）：
eval("data = {userId: 7, actionId: 36 " + (myCondition ? ", express: true}" : "}"))
Conditional definition(don't really know how to label this one):
条件定义（真的不知道如何标记这个）：
data = (
(myCondition && { userId: 7, actionId: 36, express: true }) ||
(!myCondition && { userId: 7, actionId: 36 })
);
采纳答案by Denys Séguret
Do it like this :
像这样做 ：
data: {
userId: 7,
actionId: 36,
express: (myCondition ? true : undefined)
}
A property whose value is undefinedisn't written when you stringifythe object to JSON.
将对象字符串化为JSONundefined时，不会写入值未写入的属性。
EDIT : It appears from the comments that there is no JSON involved in fact. OP is using $.ajaxso $.paramis probably used. $.param, unfortunately, does create an entry for properties whose value is undefined. So there's probably no solution without any supplementary line of code.
编辑：从评论看来，实际上没有涉及 JSON。OP 正在使用$.ajax所以$.param可能使用。$.param不幸的是，它确实为值为 的属性创建了一个条目undefined。因此，如果没有任何补充代码行，可能就没有解决方案。
回答by ericsoco
Use the spread operator.
使用扩展运算符。
data: {
userId: 7,
actionId: 36,
...myCondition && {express: true}
}
Note that if you're using Flow, that syntax might generate type check errors. You can write the above more explicitly, and less succinctly, as:
请注意，如果您使用Flow，则该语法可能会生成类型检查错误。您可以更明确、更简洁地编写上述内容，如下所示：
data: {
userId: 7,
actionId: 36,
...(myCondition ? {express: true} : {})
}
回答by Paul
You can do it if you define your object using an anonymous function instead of object literal notation:
如果您使用匿名函数而不是对象文字表示法定义对象，则可以这样做：
var data = new function(){
this.userId = 7;
this.actionId = 36;
myCondition && (this.express = true);
};
The resulting dataobject is the exact same, except it's constructorwill be the anonymous function instead of window.Object.
结果data对象完全相同，除了它将constructor是匿名函数而不是window.Object.
回答by Chris Kessel
You could do something like this:
你可以这样做：
var json = JSON.stringify( {
data: {
userId: 7,
actionId: 36,
express: (myCondition ? true : null)
}
});
回答by x4rf41
first of all, thats javascript, not JSON.
首先，那是 javascript，而不是 JSON。
the solution:
解决方案：
data: {
userId: 7,
actionId: 36
}
if(myCondition) data["express"] = true;
回答by Imad El Hitti
A bit old but there is a good solution as well you can do :
有点旧，但也有一个很好的解决方案，您可以这样做：
data: {
userId: 7,
actionId: 36
}
Object.assign(data, !myCondition && { express: yourValue });
Thus it will assign your express property with the value you need if your condition is false.
因此，如果您的条件为假，它将为您的 express 属性分配您需要的值。
