Source: \countBy.js
import baseAssignValue from './.internal/baseAssignValue.js'
import reduce from './reduce.js'
/** Used to check objects for own properties. */
const hasOwnProperty = Object.prototype.hasOwnProperty
/**
* 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).
*
* @since 0.5.0
* @category Collection
* @param {Array|Object} collection The collection to iterate over.
* @param {Function} iteratee The iteratee to transform keys.
* @returns {Object} Returns the composed aggregate object.
* @example
*
* countBy([6.1, 4.2, 6.3], Math.floor)
* // => { '4': 1, '6': 2 }
*/
function countBy(collection, iteratee) {
return reduce(collection, (result, value, key) => {
key = iteratee(value)
if (hasOwnProperty.call(result, key)) {
++result[key]
} else {
baseAssignValue(result, key, 1)
}
return result
}, {})
}
export default countBy