Source: \transform.js
import arrayEach from './.internal/arrayEach.js'
import baseForOwn from './.internal/baseForOwn.js'
import isBuffer from './isBuffer.js'
import isObject from './isObject.js'
import isTypedArray from './isTypedArray.js'
/**
* An alternative to `reduce` this method transforms `object` to a new
* `accumulator` object which is the result of running each of its own
* enumerable string keyed properties thru `iteratee`, with each invocation
* potentially mutating the `accumulator` object. If `accumulator` is not
* provided, a new object with the same `[[Prototype]]` will be used. The
* iteratee is invoked with four arguments: (accumulator, value, key, object).
* Iteratee functions may exit iteration early by explicitly returning `false`.
*
* @since 1.3.0
* @category Object
* @param {Object} object The object to iterate over.
* @param {Function} iteratee The function invoked per iteration.
* @param {*} [accumulator] The custom accumulator value.
* @returns {*} Returns the accumulated value.
* @see reduce, reduceRight
* @example
*
* transform([2, 3, 4], (result, n) => {
* result.push(n *= n)
* return n % 2 == 0
* }, [])
* // => [4, 9]
*
* transform({ 'a': 1, 'b': 2, 'c': 1 }, (result, value, key) => {
* (result[value] || (result[value] = [])).push(key)
* }, {})
* // => { '1': ['a', 'c'], '2': ['b'] }
*/
function transform(object, iteratee, accumulator) {
const isArr = Array.isArray(object)
const isArrLike = isArr || isBuffer(object) || isTypedArray(object)
if (accumulator == null) {
const Ctor = object && object.constructor
if (isArrLike) {
accumulator = isArr ? new Ctor : []
}
else if (isObject(object)) {
accumulator = typeof Ctor == 'function'
? Object.create(Object.getPrototypeOf(object))
: {}
}
else {
accumulator = {}
}
}
(isArrLike ? arrayEach : baseForOwn)(object, (value, index, object) =>
iteratee(accumulator, value, index, object))
return accumulator
}
export default transform