Middleware for backbone.sync

sync.js

define(['backbone'], function (Backbone) {
    "use strict";

    var middleware = [],
        BackboneSync = Backbone.sync;

    function passThroughMiddlewares(list, data, done) {
        if (0 === list.length) {
            done(null, data);
            return;
        }
        var cb = list.shift();

        cb.call(data.scope, data.method, data.model, data.options, function (err, method, model, options) {
            if (err) {
                throw err;
            }

            var modifiedData = {
                scope: data.scope,
                method: method,
                model: model,
                options: options
            };

            passThroughMiddlewares(list, modifiedData, done);
        });
    }

    Backbone.sync = function (method, model, options) {
        var list = middleware.slice(),

            data = {
                scope: this,
                method: method,
                model: model,
                options: options
            };

        passThroughMiddlewares(list, data, function (err, data) {
            BackboneSync.call(data.scope, data.method, data.model, data.options);
        });
    };

    return {
        addHandler: function (cb) {
            middleware.push(cb);
        },

        removeHandler: function (cb) {
            var index = middleware.indexOf(cb);

            if (index > -1) {
                middleware.splice(index, 1);
            }
        },

        removeAllHandlers: function () {
            middleware.length = 0;
        },

        getHandlersCount: function () {
            return middleware.length;
        }
    };
});