map.js
 1  'use strict';
 2  
 3  var forEach = require('./for-each');
 4  
 5  module.exports = function (obj, cb) {
 6  	var o = {};
 7  	forEach(obj, function (value, key) {
 8  		o[key] = cb.call(this, value, key, obj);
 9  	}, arguments[2]);
10  	return o;
11  };