1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
var arrayEach = require('./_arrayEach'),
baseCreate = require('./_baseCreate'),
baseForOwn = require('./_baseForOwn'),
baseIteratee = require('./_baseIteratee'),
getPrototype = require('./_getPrototype'),
isArray = require('./isArray'),
isBuffer = require('./isBuffer'),
isFunction = require('./isFunction'),
isObject = require('./isObject'),
isTypedArray = require('./isTypedArray');
/**
* 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`.
*
* @static
* @memberOf _
* @since 1.3.0
* @category Object
* @param {Object} object The object to iterate over.
* @param {Function} [iteratee=_.identity] The function invoked per iteration.
* @param {*} [accumulator] The custom accumulator value.
* @returns {*} Returns the accumulated value.
* @example
*
* _.transform([2, 3, 4], function(result, n) {
* result.push(n *= n);
* return n % 2 == 0;
* }, []);
* // => [4, 9]
*
* _.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
* (result[value] || (result[value] = [])).push(key);
* }, {});
* // => { '1': ['a', 'c'], '2': ['b'] }
*/
function transform(object, iteratee, accumulator) {
var isArr = isArray(object),
isArrLike = isArr || isBuffer(object) || isTypedArray(object);
iteratee = baseIteratee(iteratee, 4);
if (accumulator == null) {
var Ctor = object && object.constructor;
if (isArrLike) {
accumulator = isArr ? new Ctor : [];
}
else if (isObject(object)) {
accumulator = isFunction(Ctor) ? baseCreate(getPrototype(object)) : {};
}
else {
accumulator = {};
}
}
(isArrLike ? arrayEach : baseForOwn)(object, function(value, index, object) {
return iteratee(accumulator, value, index, object);
});
return accumulator;
}
module.exports = transform;
|
