Javascript AOP libraries [closed]

Answer 1

Have you seen meld.js and aop.js from https://github.com/cujojs?

SpringSource provides AOP functionality there, in addition to a bunch of other useful things for advanced Javascript programmers.

Disclaimer: I work for SpringSource.

Answer 2

Based on dotvoid solution, I created my own version of JS AOP for my own projects needs. I basically want to minimize the aspect setup costs, so I added aspect setup functionality at Function.prototype.

Function.prototype.applyBefore = function (aspect, targetFuncNames) {
....
}

I also need to support aync callbacks, such as supporting authentication and authorization for certain methods. For example:

var authenticateAspect = function (error, success, context, args) {
    logger.log('authenticate (applyBefore async) aspect is being called');
    var request = $.ajax({
        url: "http://localhost/BlogWeb/api/user/authenticate",
        type: "GET",
        data: { username:'jeff', pwd:'jeff' },
        success: function (data) {
            if (data) {
                success();
            } else {
                error();
            }
        },
        error: error
    });
    return request;
};

Person.applyBefore(authenticateAspect, 'sendNotification');

var p1 = new Person();

p1.sendNotification();

To implement this, I need to run the security and and continue upon success or stop execution on failure.

var invalidAspect = new Error("Missing a valid aspect. Aspect is not a function."),
    invalidMethod = new Error("Missing valid method to apply aspect on.");

///Parameters: aspect - defines the methods we want call before or/and 
///             after each method call ob target obejct
///            targetFuncNames - target function names to apply aspects
///Return: it should return a new object with all aspects setup on target object
Function.prototype.applyBefore = function (aspect, targetFuncNames) {
    if (typeof (aspect) != 'function')
        throw invalidAspect;

    if (typeof (targetFuncNames) != 'object')
        targetFuncNames = Array(targetFuncNames);

    var targetObj = this;
    //error handling function

    // Copy the properties over onto the new prototype
    for (var i = 0, len = targetFuncNames.length; i < len; i++) {
        var funcName = targetFuncNames[i];
        var targetFunc = targetObj.prototype[funcName];

        if (!targetFunc)
            throw invalidMethod;


        targetObj.prototype[funcName] = function () {
            var self = this, args = arguments;
            var success = function() {
                return targetFunc.apply(self, args);
            };
            var error = function () {
                logger.log('applyBefore aspect failed to pass');
                //log the error and throw new error
                throw new Error('applyBefore aspect failed to pass');
            };

            var aspectResult = aspect.apply(null, Array.prototype.concat([error, success, self], args));
            return aspectResult;
        };
    }
};

Full implementation can be found at http://www.jeffjin.net/aop-with-javascript

Answer 3

Here is what I found until now :

• dotvoid's implementation, clean syntax, nice to use, the article is a good introduction on why/how to use the given code, supports introductions, but is bugged,
• Dojo has what seems to be a good built-in implementation in dojox, here is a nice introduction on how to use it,
• there is a plugin for jQuery, jquery-aop, with a rougher syntax, passing objects and methods in a javascript object,
• AspectJS with an even rougher syntax (need to pass type of pointcut as arguments to a single method)

Like I said, dotvoid's code did not work. I corrected a little and got something that seems to work better :

InvalidAspect = new Error("Missing a valid aspect. Aspect is not a function.");
InvalidObject = new Error("Missing valid object or an array of valid objects.");
InvalidMethod = new Error("Missing valid method to apply aspect on.");

function doBefore(beforeFunc,func){
    return function(){
        beforeFunc.apply(this,arguments);
        return func.apply(this,arguments);
    };  
}

function doAfter(func, afterFunc){
    return function(){
        var res = func.apply(this,arguments);
        afterFunc.apply(this,arguments);
        return res;   
    };
}

Aspects = function(){};
Aspects.prototype={
    _addIntroduction : function(intro, obj){
         for (var m in intro.prototype) {
              obj.prototype[m] = intro.prototype[m];
            }
        },

    addIntroduction : function(aspect, objs){
        var oType = typeof(objs);

        if (typeof(aspect) != 'function')
        throw(InvalidAspect);

        if (oType == 'function'){
            this._addIntroduction(aspect, objs);
        }
        else if (oType == 'object'){
            for (var n = 0; n < objs.length; n++){
                this._addIntroduction(aspect, objs[n]);
            }
        }
        else{
            throw InvalidObject;
        }
    },

    addBefore : function(aspect, obj, funcs){
          var fType = typeof(funcs);

          if (typeof(aspect) != 'function')
            throw(InvalidAspect);

          if (fType != 'object')
            funcs = Array(funcs);

          for (var n = 0; n < funcs.length; n++){
            var fName = funcs[n];
            var old = obj.prototype[fName];

            if (!old)
              throw InvalidMethod;

            var res = doBefore(aspect,old)
            obj.prototype[fName] = res;
        }
    },

    addAfter : function(aspect, obj, funcs) {
          if (typeof(aspect) != 'function')
            throw InvalidAspect;

          if (typeof(funcs) != 'object')
            funcs = Array(funcs);

          for (var n = 0; n < funcs.length; n++)
          {
            var fName = funcs[n];
            var old = obj.prototype[fName];

            if (!old)
              throw InvalidMethod;

            var res = doAfter(old,aspect);
            obj.prototype[fName] = res;
          }
        },

    addAround : function(aspect, obj, funcs){
          if (typeof(aspect) != 'function')
            throw InvalidAspect;

          if (typeof(funcs) != 'object')
            funcs = Array(funcs);

          for (var n = 0; n < funcs.length; n++)
          {
            var fName = funcs[n];
            var old = obj.prototype[fName];
            if (!old)
              throw InvalidMethod;

            var res = aspect(old);
            obj.prototype[fName] = res;
          }

          return true;
        }
}