transform.js (2280B)
1 var arrayEach = require('./_arrayEach'), 2 baseCreate = require('./_baseCreate'), 3 baseForOwn = require('./_baseForOwn'), 4 baseIteratee = require('./_baseIteratee'), 5 getPrototype = require('./_getPrototype'), 6 isArray = require('./isArray'), 7 isBuffer = require('./isBuffer'), 8 isFunction = require('./isFunction'), 9 isObject = require('./isObject'), 10 isTypedArray = require('./isTypedArray'); 11 12 /** 13 * An alternative to `_.reduce`; this method transforms `object` to a new 14 * `accumulator` object which is the result of running each of its own 15 * enumerable string keyed properties thru `iteratee`, with each invocation 16 * potentially mutating the `accumulator` object. If `accumulator` is not 17 * provided, a new object with the same `[[Prototype]]` will be used. The 18 * iteratee is invoked with four arguments: (accumulator, value, key, object). 19 * Iteratee functions may exit iteration early by explicitly returning `false`. 20 * 21 * @static 22 * @memberOf _ 23 * @since 1.3.0 24 * @category Object 25 * @param {Object} object The object to iterate over. 26 * @param {Function} [iteratee=_.identity] The function invoked per iteration. 27 * @param {*} [accumulator] The custom accumulator value. 28 * @returns {*} Returns the accumulated value. 29 * @example 30 * 31 * _.transform([2, 3, 4], function(result, n) { 32 * result.push(n *= n); 33 * return n % 2 == 0; 34 * }, []); 35 * // => [4, 9] 36 * 37 * _.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) { 38 * (result[value] || (result[value] = [])).push(key); 39 * }, {}); 40 * // => { '1': ['a', 'c'], '2': ['b'] } 41 */ 42 function transform(object, iteratee, accumulator) { 43 var isArr = isArray(object), 44 isArrLike = isArr || isBuffer(object) || isTypedArray(object); 45 46 iteratee = baseIteratee(iteratee, 4); 47 if (accumulator == null) { 48 var Ctor = object && object.constructor; 49 if (isArrLike) { 50 accumulator = isArr ? new Ctor : []; 51 } 52 else if (isObject(object)) { 53 accumulator = isFunction(Ctor) ? baseCreate(getPrototype(object)) : {}; 54 } 55 else { 56 accumulator = {}; 57 } 58 } 59 (isArrLike ? arrayEach : baseForOwn)(object, function(value, index, object) { 60 return iteratee(accumulator, value, index, object); 61 }); 62 return accumulator; 63 } 64 65 module.exports = transform;