WinJS.Class from base.js in the Metro Web App Template

WinJS.Class.js

/* 
  © Microsoft. All rights reserved. 
*/

(function (global, undefined) { 
 
    function initializeProperties(target, members) { 
        var keys = Object.keys(members); 
        var properties; 
        var i, len; 
        for (i = 0, len = keys.length; i < len; i++) { 
            var key = keys[i]; 
            var enumerable = key.charCodeAt(0) !== /*_*/95; 
            var member = members[key]; 
            if (member && typeof member === 'object') { 
                if (member.value !== undefined || typeof member.get === 'function' || typeof member.set === 'function') { 
                    if (member.enumerable === undefined) { 
                        member.enumerable = enumerable; 
                    } 
                    properties = properties || {}; 
                    properties[key] = member; 
                    continue; 
                }  
            } 
            if (!enumerable) { 
                properties = properties || {}; 
                properties[key] = { value: member, enumerable: enumerable, configurable: true, writable: true } 
                continue; 
            } 
            target[key] = member; 
        } 
        if (properties) { 
            Object.defineProperties(target, properties); 
        } 
    } 
 
    (function (rootNamespace) { 
 
        // Create the rootNamespace in the global namespace 
        if (!global[rootNamespace]) { 
            global[rootNamespace] = Object.create(Object.prototype); 
        } 
 
        // Cache the rootNamespace we just created in a local variable 
        var _rootNamespace = global[rootNamespace]; 
        if (!_rootNamespace.Namespace) { 
            _rootNamespace.Namespace = Object.create(Object.prototype); 
        } 
 
        function defineWithParent(parentNamespace, name, members) { 
            /// <summary locid="1"> 
            /// Defines a new namespace with the specified name, under the specified parent namespace. 
            /// </summary> 
            /// <param name="parentNamespace" type="Object" locid="2"> 
            /// The parent namespace which will contain the new namespace. 
            /// </param> 
            /// <param name="name" type="String" locid="3"> 
            /// Name of the new namespace. 
            /// </param> 
            /// <param name="members" type="Object" locid="4"> 
            /// Members in the new namespace. 
            /// </param> 
            /// <returns locid="5"> 
            /// The newly defined namespace. 
            /// </returns> 
            var currentNamespace = parentNamespace, 
                namespaceFragments = name.split("."); 
 
            for (var i = 0, len = namespaceFragments.length; i < len; i++) { 
                var namespaceName = namespaceFragments[i]; 
                if (!currentNamespace[namespaceName]) { 
                    Object.defineProperty(currentNamespace, namespaceName,  
                        { value: {}, writable: false, enumerable: true, configurable: true } 
                    ); 
                } 
                currentNamespace = currentNamespace[namespaceName]; 
            } 
 
            if (members) { 
                initializeProperties(currentNamespace, members); 
            } 
 
            return currentNamespace; 
        }; 
 
        function define(name, members) { 
            /// <summary locid="6"> 
            /// Defines a new namespace with the specified name. 
            /// </summary> 
            /// <param name="name" type="String" locid="7"> 
            /// Name of the namespace.  This could be a dot-separated nested name. 
            /// </param> 
            /// <param name="members" type="Object" locid="4"> 
            /// Members in the new namespace. 
            /// </param> 
            /// <returns locid="5"> 
            /// The newly defined namespace. 
            /// </returns> 
            return defineWithParent(global, name, members); 
        } 
 
        // Establish members of the "WinJS.Namespace" namespace 
        Object.defineProperties(_rootNamespace.Namespace, { 
 
            defineWithParent: { value: defineWithParent, writable: true, enumerable: true }, 
 
            define: { value: define, writable: true, enumerable: true } 
 
        }); 
 
    })("WinJS"); 
 
    (function (WinJS) { 
 
        function define(constructor, instanceMembers, staticMembers) { 
            /// <summary locid="8"> 
            /// Defines a class using the given constructor and with the specified instance members. 
            /// </summary> 
            /// <param name="constructor" type="Function" locid="9"> 
            /// A constructor function that will be used to instantiate this class. 
            /// </param> 
            /// <param name="instanceMembers" type="Object" locid="10"> 
            /// The set of instance fields, properties and methods to be made available on the class. 
            /// </param> 
            /// <param name="staticMembers" type="Object" locid="11"> 
            /// The set of static fields, properties and methods to be made available on the class. 
            /// </param> 
            /// <returns type="Function" locid="12"> 
            /// The newly defined class. 
            /// </returns> 
            constructor = constructor || function () { }; 
            if (instanceMembers) { 
                initializeProperties(constructor.prototype, instanceMembers); 
            } 
            if (staticMembers) { 
                initializeProperties(constructor, staticMembers); 
            } 
            return constructor; 
        } 
 
        function derive(baseClass, constructor, instanceMembers, staticMembers) { 
            /// <summary locid="13"> 
            /// Uses prototypal inheritance to create a sub-class based on the supplied baseClass parameter. 
            /// </summary> 
            /// <param name="baseClass" type="Function" locid="14"> 
            /// The class to inherit from. 
            /// </param> 
            /// <param name="constructor" type="Function" locid="9"> 
            /// A constructor function that will be used to instantiate this class. 
            /// </param> 
            /// <param name="instanceMembers" type="Object" locid="10"> 
            /// The set of instance fields, properties and methods to be made available on the class. 
            /// </param> 
            /// <param name="staticMembers" type="Object" locid="11"> 
            /// The set of static fields, properties and methods to be made available on the class. 
            /// </param> 
            /// <returns type="Function" locid="12"> 
            /// The newly defined class. 
            /// </returns> 
            if (baseClass) { 
                constructor = constructor || function () { }; 
                var basePrototype = baseClass.prototype; 
                constructor.prototype = Object.create(basePrototype); 
                Object.defineProperty(constructor.prototype, "_super", { value: basePrototype }); 
                Object.defineProperty(constructor.prototype, "constructor", { value: constructor }); 
                if (instanceMembers) { 
                    initializeProperties(constructor.prototype, instanceMembers); 
                } 
                if (staticMembers) { 
                    initializeProperties(constructor, staticMembers); 
                } 
                return constructor; 
            } else { 
                return define(constructor, instanceMembers, staticMembers); 
            } 
        } 
 
        function mix(constructor) { 
            /// <summary locid="15"> 
            /// Defines a class using the given constructor and the union of the set of instance members 
            /// specified by all the mixin objects.  The mixin parameter list can be of variable length. 
            /// </summary> 
            /// <param name="constructor" locid="9"> 
            /// A constructor function that will be used to instantiate this class. 
            /// </param> 
            /// <returns locid="12"> 
            /// The newly defined class. 
            /// </returns> 
            constructor = constructor || function () { }; 
            var i, len; 
            for (i = 0, len = arguments.length; i < len; i++) { 
                initializeProperties(constructor.prototype, arguments[i]); 
            } 
            return constructor; 
        } 
 
        // Establish members of "WinJS.Class" namespace 
        WinJS.Namespace.define("WinJS.Class", { 
            define: define, 
            derive: derive, 
            mix: mix 
        }); 
 
    })(WinJS); 
 
})(this);