Function to define a namespace in JavaScript.

namespace.js

/*
 * Copyright (C) 2015 Neo Visionaries Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Source Code Location:
 *
 * namespace.js
 * https://gist.github.com/TakahikoKawasaki/97f23cdd26b5b1a681d1
 */

/**
 * Define a namespace.
 *
 * If 'aaa.bbb.ccc' is given, aaa.bbb.ccc is created if it does not exist yet.
 * The hash object that represents the last layer is returned. For example,
 * if 'aaa.bbb.ccc' is given, the hash object that represents ccc is returned.
 *
 * Usage:
 *
 *     // Define a namespace 'aaa.bbb.ccc' and add a function 'hello'
 *     // under the namespace which prints 'Hello, world.'.
 *     namespace('aaa.bbb.ccc').hello = function() {
 *         print('Hello, world.');
 *     };
 *
 *     // Execute the function.
 *     aaa.bbb.ccc.hello();
 */
namespace = function(packageName)
{
    // Local variables.
    var layers, layer, currentLayer, i;

    // Split the given string into an array.
    // Each element represents a namespace layer.
    layers = packageName.split('.');

    // If the top layer does not exist in the global namespace.
    if (eval("typeof " + layers[0]) === 'undefined')
    {
        // Define the top layer in the global namesapce.
        eval(layers[0] + " = {};");
    }

    // Assign the top layer to 'currentLayer'.
    eval("currentLayer = " + layers[0] + ";");

    for (i = 1; i < layers.length; ++i)
    {
        // A layer name.
        layer = layers[i];

        // If the layer does not exist under the current layer.
        if (!(layer in currentLayer))
        {
            // Add the layer under the current layer.
            currentLayer[layer] = {};
        }

        // Down to the next layer.
        currentLayer = currentLayer[layer];
    }

    // Return the hash object that represents the last layer.
    return currentLayer;
};