在Javascript中，如何有条件地将成员添加到对象？ [英] In Javascript, how to conditionally add a member to an object?

问题描述

我想创建一个有条件添加成员的对象。
简单的方法是：

I would like to create an object with a member added conditionally. The simple approach is:

var a = {};
if (someCondition)
    a.b = 5;

现在，我想写一个更惯用的代码。我正在尝试：

Now, I would like to write a more idiomatic code. I am trying:

a = {
    b: (someCondition? 5 : undefined)
};

但现在， b 是其成员 a ，其值为 undefined 。这不是理想的结果。

But now, b is a member of a whose value is undefined. This is not the desired result.

是否有方便的解决方案？

Is there a handy solution?

更新

我寻求一个可以处理几个成员的一般情况的解决方案。

I seek for a solution that could handle the general case with several members.

a = {
  b: (conditionB? 5 : undefined),
  c: (conditionC? 5 : undefined),
  d: (conditionD? 5 : undefined),
  e: (conditionE? 5 : undefined),
  f: (conditionF? 5 : undefined),
  g: (conditionG? 5 : undefined),
 };

推荐答案

在纯粹的Javascript中，我想不出任何更具风格的东西比你的第一个代码片段。

In pure Javascript, I cannot think of anything more idiomatic than your first code snippet.

然而，如果使用jQuery库并不是不可能的话，那么 $ .extend（）应该符合您的要求，因为文档说：

If, however, using the jQuery library is not out of the question, then $.extend() should meet your requirements because, as the documentation says:

未复制未定义的属性。

Undefined properties are not copied.

因此，您可以写：

var a = $.extend({}, {
    b: conditionB ? 5 : undefined,
    c: conditionC ? 5 : undefined,
    // and so on...
});

并获得您期望的结果（如果 conditionB false ，然后 b 将不存在于 a 中）。

And obtain the results you expect (if conditionB is false, then b will not exist in a).

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