The Tor Browser / file revision

 "use strict";

 var defineProperty = Object.defineProperty || function(object, name, property) {

   object[name] = property.value

   return object

 }

 // Shortcut for `Object.prototype.toString` for faster access.

 var typefy = Object.prototype.toString

 // Map to for jumping from typeof(value) to associated type prefix used

 // as a hash in the map of builtin implementations.

 var types = { "function": "Object", "object": "Object" }

 // Array is used to save method implementations for the host objects in order

 // to avoid extending them with non-primitive values that could cause leaks.

 var host = []

 // Hash map is used to save method implementations for builtin types in order

 // to avoid extending their prototypes. This also allows to share method

 // implementations for types across diff contexts / frames / compartments.

 var builtin = {}

 function Primitive() {}

 function ObjectType() {}

 ObjectType.prototype = new Primitive()

 function ErrorType() {}

 ErrorType.prototype = new ObjectType()

 var Default = builtin.Default = Primitive.prototype

 var Null = builtin.Null = new Primitive()

 var Void = builtin.Void = new Primitive()

 builtin.String = new Primitive()

 builtin.Number = new Primitive()

 builtin.Boolean = new Primitive()

 builtin.Object = ObjectType.prototype

 builtin.Error = ErrorType.prototype

 builtin.EvalError = new ErrorType()

 builtin.InternalError = new ErrorType()

 builtin.RangeError = new ErrorType()

 builtin.ReferenceError = new ErrorType()

 builtin.StopIteration = new ErrorType()

 builtin.SyntaxError = new ErrorType()

 builtin.TypeError = new ErrorType()

 builtin.URIError = new ErrorType()

 function Method(hint) {

   /**

   Private Method is a callable private name that dispatches on the first

   arguments same named Method:

       method(object, ...rest) => object[method](...rest)

   Optionally hint string may be provided that will be used in generated names

   to ease debugging.

   ## Example

       var foo = Method()

       // Implementation for any types

       foo.define(function(value, arg1, arg2) {

         // ...

       })

       // Implementation for a specific type

       foo.define(BarType, function(bar, arg1, arg2) {

         // ...

       })

   **/

   // Create an internal unique name if `hint` is provided it is used to

   // prefix name to ease debugging.

   var name = (hint || "") + "#" + Math.random().toString(32).substr(2)

   function dispatch(value) {

     // Method dispatches on type of the first argument.

     // If first argument is `null` or `void` associated implementation is

     // looked up in the `builtin` hash where implementations for built-ins

     // are stored.

     var type = null

     var method = value === null ? Null[name] :

                  value === void(0) ? Void[name] :

                  // Otherwise attempt to use method with a generated private

                  // `name` that is supposedly in the prototype chain of the

                  // `target`.

                  value[name] ||

                  // Otherwise assume it's one of the built-in type instances,

                  // in which case implementation is stored in a `builtin` hash.

                  // Attempt to find a implementation for the given built-in

                  // via constructor name and method name.

                  ((type = builtin[(value.constructor || "").name]) &&

                   type[name]) ||

                  // Otherwise assume it's a host object. For host objects

                  // actual method implementations are stored in the `host`

                  // array and only index for the implementation is stored

                  // in the host object's prototype chain. This avoids memory

                  // leaks that otherwise could happen when saving JS objects

                  // on host object.

                  host[value["!" + name] || void(0)] ||

                  // Otherwise attempt to lookup implementation for builtins by

                  // a type of the value. This basically makes sure that all

                  // non primitive values will delegate to an `Object`.

                  ((type = builtin[types[typeof(value)]]) && type[name])

     // If method implementation for the type is still not found then

     // just fallback for default implementation.

     method = method || Default[name]

     // If implementation is still not found (which also means there is no

     // default) just throw an error with a descriptive message.

     if (!method) throw TypeError("Type does not implements method: " + name)

     // If implementation was found then just delegate.

     return method.apply(method, arguments)

   }

   // Make `toString` of the dispatch return a private name, this enables

   // method definition without sugar:

   //

   //    var method = Method()

   //    object[method] = function() { /***/ }

   dispatch.toString = function toString() { return name }

   // Copy utility methods for convenient API.

   dispatch.implement = implementMethod

   dispatch.define = defineMethod

   return dispatch

 }

 // Create method shortcuts form functions.

 var defineMethod = function defineMethod(Type, lambda) {

   return define(this, Type, lambda)

 }

 var implementMethod = function implementMethod(object, lambda) {

   return implement(this, object, lambda)

 }

 // Define `implement` and `define` polymorphic methods to allow definitions

 // and implementations through them.

 var implement = Method("implement")

 var define = Method("define")

 function _implement(method, object, lambda) {

   /**

   Implements `Method` for the given `object` with a provided `implementation`.

   Calling `Method` with `object` as a first argument will dispatch on provided

   implementation.

   **/

   return defineProperty(object, method.toString(), {

     enumerable: false,

     configurable: false,

     writable: false,

     value: lambda

   })

 }

 function _define(method, Type, lambda) {

   /**

   Defines `Method` for the given `Type` with a provided `implementation`.

   Calling `Method` with a first argument of this `Type` will dispatch on

   provided `implementation`. If `Type` is a `Method` default implementation

   is defined. If `Type` is a `null` or `undefined` `Method` is implemented

   for that value type.

   **/

   // Attempt to guess a type via `Object.prototype.toString.call` hack.

   var type = Type && typefy.call(Type.prototype)

   // If only two arguments are passed then `Type` is actually an implementation

   // for a default type.

   if (!lambda) Default[method] = Type

   // If `Type` is `null` or `void` store implementation accordingly.

   else if (Type === null) Null[method] = lambda

   else if (Type === void(0)) Void[method] = lambda

   // If `type` hack indicates built-in type and type has a name us it to

   // store a implementation into associated hash. If hash for this type does

   // not exists yet create one.

   else if (type !== "[object Object]" && Type.name) {

     var Bulitin = builtin[Type.name] || (builtin[Type.name] = new ObjectType())

     Bulitin[method] = lambda

   }

   // If `type` hack indicates an object, that may be either object or any

   // JS defined "Class". If name of the constructor is `Object`, assume it's

   // built-in `Object` and store implementation accordingly.

   else if (Type.name === "Object")

     builtin.Object[method] = lambda

   // Host objects are pain!!! Every browser does some crazy stuff for them

   // So far all browser seem to not implement `call` method for host object

   // constructors. If that is a case here, assume it's a host object and

   // store implementation in a `host` array and store `index` in the array

   // in a `Type.prototype` itself. This avoids memory leaks that could be

   // caused by storing JS objects on a host objects.

   else if (Type.call === void(0)) {

     var index = host.indexOf(lambda)

     if (index < 0) index = host.push(lambda) - 1

     // Prefix private name with `!` so it can be dispatched from the method

     // without type checks.

     implement("!" + method, Type.prototype, index)

   }

   // If Got that far `Type` is user defined JS `Class`. Define private name

   // as hidden property on it's prototype.

   else

     implement(method, Type.prototype, lambda)

 }

 // And provided implementations for a polymorphic equivalents.

 _define(define, _define)

 _define(implement, _implement)

 // Define exports on `Method` as it's only thing being exported.

 Method.implement = implement

 Method.define = define

 Method.Method = Method

 Method.method = Method

 Method.builtin = builtin

 Method.host = host

 module.exports = Method