lodash_mixins.js

/**
 *
 * Here we will could extend lodash with some custom useful methods
 *
 */
(function (_) {
        'use strict';
	/**
	 * Initialize a new array having a custom length and a custom default value
	 * @param  { Number | Object | String } defaultValue: any valid javascript element
	 * @param  { Int } length: the length of the output
	 * @return { Array } having a custom value and custom length
	 */
	var CustomArray = function (defaultValue, length) {
		var _arr = [];
		while (length--) _arr.push(defaultValue);
		return _arr;
	};
	var _arrOperation = function (arr1, arr2, operation) {
		var arr2 = arr2 || arr1;
		if (_.isNumber(arr2)) arr2 = new CustomArray(arr2, arr1.length);
		if (_.isNumber(arr1)) arr1 = new CustomArray(arr1, arr2.length);
		if (arr1.length !== arr2.length) throw ('Please the two arrays must have the same length');

		return _.map(arr1, function (val, i) {
			switch (operation) {
			case 'max':
				return val > arr2[i] ? val : arr2[i];
				break;
			case 'min':
				return val < arr2[i] ? val : arr2[i];
				break;
			case '+':
				return val + arr2[i];
				break;
			case '*':
				return val * arr2[i];
				break;
			case '/':
				return val / arr2[i];
				break;
			default:
			}
		});
	};
	_.mixin({
		/**
		 *
		 * Similar to the _.pick method but it could be used with more than one property
		 * @return { Object } new object containing only the properties filtered
		 *
		 */
		'multiplePick': function (obj, array) {
			var ret = {};
			_.each(array, function (key) {
				ret[key] = obj[key];
			});
			return ret;
		},
		/**
		 *
		 * @param  { Array } arr
		 * @param  { Array | Object | String | Number } elm: element contained inside this array
		 * @return { Boolean } return whether the element is the last one of the array
		 */
		'isLast': function (arr, elm) {
			var length = arr.length - 1,
				elmIndex = _.indexOf(arr, elm);
			// if this element is not contained iside this array
			if (!~elmIndex) return false;

			return elmIndex === length;
		},
		/**
		 * Merge two arrays picking the max numeric value per each index
		 * @param  { Array } arr1
		 * @param  { Array } arr2
		 * @return { Array }
		 */
		'arrMax': function (arr1, arr2) {
			return _arrOperation(arr1, arr2, 'max');
		},
		/**
		 * Return the sum of all the numeric items in the first array or merge two numeric arrays summing the value of each index of these last
		 * @param  { Array } arr1
		 * @param  { Array } arr2
		 * @return { Float }
		 */
		'arrSum': function (arr1, arr2) {
			return _arrOperation(arr1, arr2, '+');
		},
		/**
		 * Multiply two array
		 * @param  { Array } arr1
		 * @param  { Array } arr2
		 * @return { Float }
		 */
		'arrMultiplication': function (arr1, arr2) {
			return _arrOperation(arr1, arr2, '*');
		},
		/**
		 * Divide two array
		 * @param  { Array } arr1
		 * @param  { Array } arr2
		 * @return { Float }
		 */
		'arrDivision': function (arr1, arr2) {
			return _arrOperation(arr1, arr2, '/');
		}
	});
}(window._));