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62 lines
2.1 KiB
JavaScript
62 lines
2.1 KiB
JavaScript
var arrayEach = require('../internal/arrayEach'),
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baseCallback = require('../internal/baseCallback'),
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baseCreate = require('../internal/baseCreate'),
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baseForOwn = require('../internal/baseForOwn'),
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isArray = require('../lang/isArray'),
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isFunction = require('../lang/isFunction'),
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isObject = require('../lang/isObject'),
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isTypedArray = require('../lang/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 enumerable
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* properties through `iteratee`, with each invocation potentially mutating
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* the `accumulator` object. The `iteratee` is bound to `thisArg` and invoked
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* with four arguments: (accumulator, value, key, object). Iteratee functions
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* 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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* @category Object
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* @param {Array|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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* @param {*} [thisArg] The `this` binding of `iteratee`.
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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 }, function(result, n, key) {
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* result[key] = n * 3;
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* });
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* // => { 'a': 3, 'b': 6 }
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*/
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function transform(object, iteratee, accumulator, thisArg) {
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var isArr = isArray(object) || isTypedArray(object);
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iteratee = baseCallback(iteratee, thisArg, 4);
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if (accumulator == null) {
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if (isArr || isObject(object)) {
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var Ctor = object.constructor;
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if (isArr) {
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accumulator = isArray(object) ? new Ctor : [];
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} else {
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accumulator = baseCreate(isFunction(Ctor) ? Ctor.prototype : undefined);
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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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(isArr ? 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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