lodash/lodash.map/index.js

/**
 * lodash 3.1.4 (Custom Build) <https://lodash.com/>
 * Build: `lodash modern modularize exports="npm" -o ./`
 * Copyright 2012-2015 The Dojo Foundation <http://dojofoundation.org/>
 * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
 * Copyright 2009-2015 Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
 * Available under MIT license <https://lodash.com/license>
 */
var arrayMap = require('lodash._arraymap'),
    baseCallback = require('lodash._basecallback'),
    baseEach = require('lodash._baseeach'),
    isArray = require('lodash.isarray');

/**
 * Used as the [maximum length](http://ecma-international.org/ecma-262/6.0/#sec-number.max_safe_integer)
 * of an array-like value.
 */
var MAX_SAFE_INTEGER = 9007199254740991;

/**
 * The base implementation of `_.map` without support for callback shorthands
 * and `this` binding.
 *
 * @private
 * @param {Array|Object|string} collection The collection to iterate over.
 * @param {Function} iteratee The function invoked per iteration.
 * @returns {Array} Returns the new mapped array.
 */
function baseMap(collection, iteratee) {
  var index = -1,
      result = isArrayLike(collection) ? Array(collection.length) : [];

  baseEach(collection, function(value, key, collection) {
    result[++index] = iteratee(value, key, collection);
  });
  return result;
}

/**
 * The base implementation of `_.property` without support for deep paths.
 *
 * @private
 * @param {string} key The key of the property to get.
 * @returns {Function} Returns the new function.
 */
function baseProperty(key) {
  return function(object) {
    return object == null ? undefined : object[key];
  };
}

/**
 * Gets the "length" property value of `object`.
 *
 * **Note:** This function is used to avoid a [JIT bug](https://bugs.webkit.org/show_bug.cgi?id=142792)
 * that affects Safari on at least iOS 8.1-8.3 ARM64.
 *
 * @private
 * @param {Object} object The object to query.
 * @returns {*} Returns the "length" value.
 */
var getLength = baseProperty('length');

/**
 * Checks if `value` is array-like.
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is array-like, else `false`.
 */
function isArrayLike(value) {
  return value != null && isLength(getLength(value));
}

/**
 * Checks if `value` is a valid array-like length.
 *
 * **Note:** This function is based on [`ToLength`](http://ecma-international.org/ecma-262/6.0/#sec-tolength).
 *
 * @private
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a valid length, else `false`.
 */
function isLength(value) {
  return typeof value == 'number' && value > -1 && value % 1 == 0 && value <= MAX_SAFE_INTEGER;
}

/**
 * Creates an array of values by running each element in `collection` through
 * `iteratee`. The `iteratee` is bound to `thisArg` and invoked with three
 * arguments: (value, index|key, collection).
 *
 * If a property name is provided for `iteratee` the created `_.property`
 * style callback returns the property value of the given element.
 *
 * If a value is also provided for `thisArg` the created `_.matchesProperty`
 * style callback returns `true` for elements that have a matching property
 * value, else `false`.
 *
 * If an object is provided for `iteratee` the created `_.matches` style
 * callback returns `true` for elements that have the properties of the given
 * object, else `false`.
 *
 * Many lodash methods are guarded to work as iteratees for methods like
 * `_.every`, `_.filter`, `_.map`, `_.mapValues`, `_.reject`, and `_.some`.
 *
 * The guarded methods are:
 * `ary`, `callback`, `chunk`, `clone`, `create`, `curry`, `curryRight`,
 * `drop`, `dropRight`, `every`, `fill`, `flatten`, `invert`, `max`, `min`,
 * `parseInt`, `slice`, `sortBy`, `take`, `takeRight`, `template`, `trim`,
 * `trimLeft`, `trimRight`, `trunc`, `random`, `range`, `sample`, `some`,
 * `sum`, `uniq`, and `words`
 *
 * @static
 * @memberOf _
 * @alias collect
 * @category Collection
 * @param {Array|Object|string} collection The collection to iterate over.
 * @param {Function|Object|string} [iteratee=_.identity] The function invoked
 *  per iteration.
 * @param {*} [thisArg] The `this` binding of `iteratee`.
 * @returns {Array} Returns the new mapped array.
 * @example
 *
 * function timesThree(n) {
 *   return n * 3;
 * }
 *
 * _.map([1, 2], timesThree);
 * // => [3, 6]
 *
 * _.map({ 'a': 1, 'b': 2 }, timesThree);
 * // => [3, 6] (iteration order is not guaranteed)
 *
 * var users = [
 *   { 'user': 'barney' },
 *   { 'user': 'fred' }
 * ];
 *
 * // using the `_.property` callback shorthand
 * _.map(users, 'user');
 * // => ['barney', 'fred']
 */
function map(collection, iteratee, thisArg) {
  var func = isArray(collection) ? arrayMap : baseMap;
  iteratee = baseCallback(iteratee, thisArg, 3);
  return func(collection, iteratee);
}

module.exports = map;