countBy

_.countBy(collection, [iteratee=_.identity])

创建一个由运行 collection 至 iteratee 的每个元素的结果生成的键组成的对象。每个键的对应值是 iteratee 返回该键的次数。迭代器使用一个参数调用：(value)。

¥Creates an object composed of keys generated from the results of running each element of collection thru iteratee. The corresponding value of each key is the number of times the key was returned by iteratee. The iteratee is invoked with one argument: (value).

新增于

¥Since

0.5.0

参数

¥Arguments

1. collection (数组|对象)：要迭代的集合。

   ¥collection (Array|Object): The collection to iterate over.

2. [iteratee=_.identity] (函数)：用于转换键的迭代器。

   ¥[iteratee=_.identity] (Function): The iteratee to transform keys.

返回

¥Returns

(对象)：返回组合的聚合对象。

¥(Object): Returns the composed aggregate object.

示例

¥Example

_.countBy([6.1, 4.2, 6.3], Math.floor);
// => { '4': 1, '6': 2 }

// The `_.property` iteratee shorthand.
_.countBy(['one', 'two', 'three'], 'length');
// => { '3': 2, '5': 1 }