map.js

var arrayMap = require('../internal/arrayMap'),
    baseCallback = require('../internal/baseCallback'),
    baseMap = require('../internal/baseMap'),
    isArray = require('../lang/isArray');

/**
 * 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;