如何使用 lodash 中的 includes 方法检查对象是否在集合中? [英] How do I use the includes method in lodash to check if an object is in the collection?

问题描述

lodash 让我使用 includes 检查基本数据类型的成员资格:

lodash lets me check for membership of basic data types with includes:

_.includes([1, 2, 3], 2)
> true

但以下方法不起作用:

_.includes([{"a": 1}, {"b": 2}], {"b": 2})
> false

这让我很困惑，因为以下搜索集合的方法似乎很好:

This confuses me because the following methods that search through a collection seem to do just fine:

_.where([{"a": 1}, {"b": 2}], {"b": 2})
> {"b": 2}
_.find([{"a": 1}, {"b": 2}], {"b": 2})
> {"b": 2}

我做错了什么?如何使用 includes 检查集合中对象的成员资格?

What am I doing wrong? How do I check for the membership of an object in a collection with includes ?

问题最初针对 lodash 2.4.1 版，已针​​对 lodash 4.0.0 更新

edit: question was originally for for lodash version 2.4.1, updated for lodash 4.0.0

推荐答案

includes(以前称为 contains 和 include)方法通过引用比较对象(或更准确地说，使用 ===).因为示例中 {"b": 2} 的两个对象字面量代表 不同 实例，所以它们不相等.注意:

The includes (formerly called contains and include) method compares objects by reference (or more precisely, with ===). Because the two object literals of {"b": 2} in your example represent different instances, they are not equal. Notice:

({"b": 2} === {"b": 2})
> false

然而，这是可行的，因为只有一个 {"b": 2}:

However, this will work because there is only one instance of {"b": 2}:

var a = {"a": 1}, b = {"b": 2};
_.includes([a, b], b);
> true

另一方面，where(已弃用在 v4) 和 find 方法根据对象的属性比较对象，所以他们不需要引用相等.作为 includes 的替代方法，您可能想尝试 some(也称为 any):

On the other hand, the where(deprecated in v4) and find methods compare objects by their properties, so they don't require reference equality. As an alternative to includes, you might want to try some (also aliased as any):

_.some([{"a": 1}, {"b": 2}], {"b": 2})
> true

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