devmeetings.pl aspect js task implementation

aspect.js

var aspect = {};

aspect.add = function (obj, fnName, aspectFn, when, once) {
    if ('object' !== typeof obj) throw new TypeError('Must pass an object as the first argument');

    obj = obj || window;

    if (Array.isArray(fnName)) {
        fnName.forEach(function (name) {
            aspect._add(obj, name, aspectFn, when, once);
        });
    } else if (fnName instanceof RegExp) {
        for (var name in obj) {
            if (fnName.test(name)) {
                aspect._add(obj, name, aspectFn, when, once);
            }
        }
    } else {
        aspect._add(obj, fnName, aspectFn, when, once);
    }
};

aspect._add = function (obj, fnName, aspectFn, when, once) {
    if (!obj[fnName]) throw new TypeError('Object doesn\'t have function named: ' + fnName);

    when = when || 'before';
    aspectFn.once = once || false;

    var currentFn = obj[fnName],
        augmentedFn;

    // Check if the function is already agumented
    if (currentFn.originalFn) {
        if (when === "before") {
            currentFn.befores.unshift(aspectFn);
        } else {
            currentFn.afters.push(aspectFn);
        }
    } else {
        augmentedFn = function () {
            augmentedFn.befores.forEach(function (beforeFn) {
                beforeFn.apply(this, arguments);
            });

            // Remove apsect functions that were supposed to run only once
            augmentedFn.befores = augmentedFn.befores.filter(function (beforeFn) {
                return !beforeFn.once;
            });

            var result = augmentedFn.originalFn.apply(this, arguments);

            augmentedFn.afters.forEach(function (afterFn) {
                afterFn.apply(this, arguments);
            });

            // Remove apsect functions that were supposed to run only once
            augmentedFn.afters = augmentedFn.afters.filter(function (afterFn) {
                return !afterFn.once;
            });

            return result;
        };

        augmentedFn.befores = [];
        augmentedFn.afters = [];
        augmentedFn.originalFn = currentFn;

        if (when === "before") {
            augmentedFn.befores.unshift(aspectFn);
        } else {
            augmentedFn.afters.push(aspectFn);
        }        

        obj[fnName] = augmentedFn;
    }
};

aspect.remove = function (obj, fnName, aspectFn, when) {
    var augmentedFn = obj[fnName], 
        type, i;

    obj = obj || window;
    when = when || 'before';
    type = when === 'before' ? 'befores' : 'afters';

    // Remove aspect function
    i = augmentedFn[type].indexOf(aspectFn);
    if (i !== -1) {
        augmentedFn[type].splice(i, 1);
    }

    // Revert function to the original one if there are no more aspect functions
    if (!augmentedFn.befores.length && !augmentedFn.afters.length) {
        obj[fnName] = augmentedFn.originalFn;
    }
};