This library defines utilities for JavaScript metaprogramming. See the specs for examples.

This library predates, and has not been updated for, ECMAScript 5's getters, setters, and Object.defineProperty method.

MOP.Object(object).accessor(propertyName)
MOP.Class(klass).accessor(propertyName)

Attaches getXXX and setXXX to object or to klass.prototype. XXX is the capitalized form of propertyName; for example, name generates getName and setName.

MOP.Object(object).getter(propertyName)
MOP.Class(klass).getter(propertyName)

Attaches getXXX to object or to klass.prototype. XXX is the capitalized form of propertyName; for example, name generates getName.

MOP.Object(object).delegate(propertyName, methods)
MOP.Class(klass).delegate(propertyName, methods)

For each name in methods, defines a method on object or klass.prototype with this name, that delegates to the method of the propertyName property of object with the same name.

MOP.Object(object).method(methodName).guardBy(guardFn)
MOP.Class(klass).method(methodName).guardBy(guardFn)

Replaces object.methodName by a method that calls the underlying method only if guardFn, applied to the same arguments, returns a true value.

MOP.Object(object).method(methodName).guardUntil(guardFn, ms)
MOP.Class(klass).method(methodName).guardUntil(guardFn, ms)

A call to object.methodName causes a timer to periodically call guardFn until it returns a true value, at which point the underlying function is called, and the timer stops.

MOP.Object(object).method(methodName).time(guardFn)
MOP.Class(klass).method(methodName).time(guardFn)

Replaces object.methodName by a method that calls the underlying function, and prints to the console the name of the method and the time it took to execute.

MOP.Object(object).method(methodName).trace(guardFn)
MOP.Class(klass).method(methodName).trace(guardFn)

Replaces object.methodName by a method that calls the underlying function, and prints to the console the name of the method and its return value.

new MOP.MethodReplacer(object, methods)

When a new MethodReplacer is constructed, it replaces each method on object by the method in methods with the same key value, if such a method exists. A MethodReplacer has a single method, restore, which restores each method to its pre-replacement value.

MOP.withMethodOverridesCallback(object, methods, k)

Calls fn on object, within a dynamic scope within which the methods in methods have temporarily replaced the like-named methods on object. The scope is terminated by the argument to the call to k; this argument should be treated as a continuation, and restores the methods.

new MOP.QueueBall(object, methodNames)

When a new QueueBall is constructed, it replaces each method named by methodNames with a method that enqueues the method call (the name of the method and its arguments). A QueueBall has a single method, replayMethodCalls, which plays back the method calls and restores the methods.

MOP.withDeferredMethods(object, methodNames, k)

Calls fn on object, within a dynamic scope within which the methods in methodNames have been enqueued. The scope is terminated by the argument to the call to k; this argument should be treated as a continuation, and ends the queue, replaying the methods.

Download from http://github.com/osteele/mop-js, or clone from

git clone http://github.com/osteele/mop-js.git

Copyright 2007-2008 by Oliver Steele. All rights reserved. Available under the MIT License.