A Javascript router in 83 LOCS (including white space).

Router.js

var Router = function(routeDef){
    this.routes = [];
    routeDef.call(this);
};

Router.prototype.splitPath = function(path){
    var splits = path.split('/');
    return _.filter(splits, function(part){
        return part !== '';
    });
};

Router.prototype.hashLocation =  function(){
    var hash = window.location.hash;
    var index = hash.indexOf('#/');
    
    if(hash === '#/'){
        return [];
    }else if(index >= 0){
        hash = hash.substring(index + 2, hash.length);
        return this.splitPath(hash);
    }else{
        return [];
    }
};

Router.prototype.findRoute = function(path){
    var self = this;
    var matchPart = function(pathPart, routePart){
        if(routePart.indexOf(':') === 0){
            self.params[routePart.substring(1)] = pathPart;
            return true;
        }else{
            return routePart === pathPart;
        }
    };
    if(path.length === 0){
        return _.find(this.routes, function(r){
            return r.path.length === 0;
        });
    }else{
        var candidates = _.filter(this.routes, function(r){
            return r.path.length === path.length;
        });

        return _.find(candidates,function(route){
            var match = true;
            for(var i = 0; i < path.length;i++){
                if(match){
                    match = matchPart(path[i],route.path[i]);
                }
            }
            return match;
        });
    }
};

Router.prototype.runRoute = function(path){
    this.params = {};
    var routeDef = this.findRoute(path);
    if(!_.isUndefined(routeDef)){
        routeDef.handler.call(this);
    }
};

Router.prototype.run = function(){
    var self = this;
    
    $(window).bind('hashchange', function() {
        self.runRoute(self.hashLocation());
    });
    
    if(window.location.hash === ''){
        window.location = window.location + '#/';
    }
    self.runRoute(self.hashLocation());
};


Router.prototype.get = function(path, handler){
    this.routes.push({path: this.splitPath(path), handler: handler});
};