| /** |
| * Lo-Dash 2.4.1 (Custom Build) <http://lodash.com/> |
| * Build: `lodash modularize exports="node" -o ./compat/` |
| * Copyright 2012-2013 The Dojo Foundation <http://dojofoundation.org/> |
| * Based on Underscore.js 1.5.2 <http://underscorejs.org/LICENSE> |
| * Copyright 2009-2013 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors |
| * Available under MIT license <http://lodash.com/license> |
| */ |
| var createAggregator = require('../internals/createAggregator'); |
| |
| /** Used for native method references */ |
| var objectProto = Object.prototype; |
| |
| /** Native method shortcuts */ |
| var hasOwnProperty = objectProto.hasOwnProperty; |
| |
| /** |
| * Creates an object composed of keys generated from the results of running |
| * each element of `collection` through the callback. The corresponding value |
| * of each key is the number of times the key was returned by the callback. |
| * The callback is bound to `thisArg` and invoked with three arguments; |
| * (value, index|key, collection). |
| * |
| * If a property name is provided for `callback` the created "_.pluck" style |
| * callback will return the property value of the given element. |
| * |
| * If an object is provided for `callback` the created "_.where" style callback |
| * will return `true` for elements that have the properties of the given object, |
| * else `false`. |
| * |
| * @static |
| * @memberOf _ |
| * @category Collections |
| * @param {Array|Object|string} collection The collection to iterate over. |
| * @param {Function|Object|string} [callback=identity] The function called |
| * per iteration. If a property name or object is provided it will be used |
| * to create a "_.pluck" or "_.where" style callback, respectively. |
| * @param {*} [thisArg] The `this` binding of `callback`. |
| * @returns {Object} Returns the composed aggregate object. |
| * @example |
| * |
| * _.countBy([4.3, 6.1, 6.4], function(num) { return Math.floor(num); }); |
| * // => { '4': 1, '6': 2 } |
| * |
| * _.countBy([4.3, 6.1, 6.4], function(num) { return this.floor(num); }, Math); |
| * // => { '4': 1, '6': 2 } |
| * |
| * _.countBy(['one', 'two', 'three'], 'length'); |
| * // => { '3': 2, '5': 1 } |
| */ |
| var countBy = createAggregator(function(result, value, key) { |
| (hasOwnProperty.call(result, key) ? result[key]++ : result[key] = 1); |
| }); |
| |
| module.exports = countBy; |