Question

Which Javascript AOP library do you use, and what are its key features ?

Answer 1

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;
        }
}