How can I run a "middleware" function before a route method is executed?

Question

Say I have a backbone router like:

routes:
  ""                          : "homepage"
  "catalog/:id"               : "catalogPage"
  "catalog/:id/products/:id2" : "productPage"

homepage   :           -> doStuff()
catalogPage: (id)      -> doOtherStuff()
productPage: (id, id2) -> doEvenMoreStuff()

and a function:

executeBefore = -> console.log("hello")

If I want executeBefore to be called and executed each time a route is called and before the corresponding route method, is there a simple way to do it apart from inserting a call to executeBefore at the beginning of every route method ?

Answer 1

You can override the route function in your router class to intercept the route calls :

var Router = Backbone.Router.extend({
    routes: {
        "" : "homepage",
        "catalog/:id" : "catalogPage"
    },

    route: function(route, name, callback) {
        var router = this;
        if (!callback) callback = this[name];

        var f = function() {
            console.log('route before', route);
            callback.apply(router, arguments);
            console.log('route after', route);
        };
        return Backbone.Router.prototype.route.call(this, route, name, f);
    },

    homepage: function() {
        console.log("homepage");
    },
    catalogPage: function(id) {
        console.log("catalogPage "+id);
    }
});

var r = new Router();
Backbone.history.start();

And a demo http://jsfiddle.net/nikoshr/EdLzh/