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66 lines
2.2 KiB
JavaScript
66 lines
2.2 KiB
JavaScript
5 years ago
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var arrayEach = require('./_arrayEach'),
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baseCreate = require('./_baseCreate'),
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baseForOwn = require('./_baseForOwn'),
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baseIteratee = require('./_baseIteratee'),
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getPrototype = require('./_getPrototype'),
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isArray = require('./isArray'),
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isBuffer = require('./isBuffer'),
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isFunction = require('./isFunction'),
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isObject = require('./isObject'),
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isTypedArray = require('./isTypedArray');
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/**
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* An alternative to `_.reduce`; this method transforms `object` to a new
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* `accumulator` object which is the result of running each of its own
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* enumerable string keyed properties thru `iteratee`, with each invocation
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* potentially mutating the `accumulator` object. If `accumulator` is not
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* provided, a new object with the same `[[Prototype]]` will be used. The
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* iteratee is invoked with four arguments: (accumulator, value, key, object).
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* Iteratee functions may exit iteration early by explicitly returning `false`.
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*
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* @static
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* @memberOf _
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* @since 1.3.0
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* @category Object
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* @param {Object} object The object to iterate over.
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* @param {Function} [iteratee=_.identity] The function invoked per iteration.
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* @param {*} [accumulator] The custom accumulator value.
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* @returns {*} Returns the accumulated value.
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* @example
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*
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* _.transform([2, 3, 4], function(result, n) {
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* result.push(n *= n);
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* return n % 2 == 0;
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* }, []);
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* // => [4, 9]
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*
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* _.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
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* (result[value] || (result[value] = [])).push(key);
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* }, {});
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* // => { '1': ['a', 'c'], '2': ['b'] }
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*/
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function transform(object, iteratee, accumulator) {
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var isArr = isArray(object),
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isArrLike = isArr || isBuffer(object) || isTypedArray(object);
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iteratee = baseIteratee(iteratee, 4);
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if (accumulator == null) {
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var Ctor = object && object.constructor;
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if (isArrLike) {
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accumulator = isArr ? new Ctor : [];
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}
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else if (isObject(object)) {
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accumulator = isFunction(Ctor) ? baseCreate(getPrototype(object)) : {};
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}
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else {
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accumulator = {};
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}
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}
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(isArrLike ? arrayEach : baseForOwn)(object, function(value, index, object) {
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return iteratee(accumulator, value, index, object);
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});
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return accumulator;
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}
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module.exports = transform;
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