Function to define a namespace in JavaScript (namespace.js)

Sample Code:

// 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(); 

Source Code:

	/*
	* 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;
	};

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