groupBy.js (1399B)
1 var baseAssignValue = require('./_baseAssignValue'), 2 createAggregator = require('./_createAggregator'); 3 4 /** Used for built-in method references. */ 5 var objectProto = Object.prototype; 6 7 /** Used to check objects for own properties. */ 8 var hasOwnProperty = objectProto.hasOwnProperty; 9 10 /** 11 * Creates an object composed of keys generated from the results of running 12 * each element of `collection` thru `iteratee`. The order of grouped values 13 * is determined by the order they occur in `collection`. The corresponding 14 * value of each key is an array of elements responsible for generating the 15 * key. The iteratee is invoked with one argument: (value). 16 * 17 * @static 18 * @memberOf _ 19 * @since 0.1.0 20 * @category Collection 21 * @param {Array|Object} collection The collection to iterate over. 22 * @param {Function} [iteratee=_.identity] The iteratee to transform keys. 23 * @returns {Object} Returns the composed aggregate object. 24 * @example 25 * 26 * _.groupBy([6.1, 4.2, 6.3], Math.floor); 27 * // => { '4': [4.2], '6': [6.1, 6.3] } 28 * 29 * // The `_.property` iteratee shorthand. 30 * _.groupBy(['one', 'two', 'three'], 'length'); 31 * // => { '3': ['one', 'two'], '5': ['three'] } 32 */ 33 var groupBy = createAggregator(function(result, value, key) { 34 if (hasOwnProperty.call(result, key)) { 35 result[key].push(value); 36 } else { 37 baseAssignValue(result, key, [value]); 38 } 39 }); 40 41 module.exports = groupBy;