How to detect invalid route and trigger function in Backbone.Controller - backbone.js

Question

Is there any method to detect invalid (or undefined) route and trigger 404 page in Backbone.Controller?
I've defined routes in my Controller like this, but it didn't work.
class MyController extends Backbone.Controller
routes:
"method_a": "methodA"
"method_b": "methodB"
"*undefined": "show404Error"
# when access to /#method_a
methodA: ->
console.log "this page exists"
# when access to /#method_b
methodB: ->
console.log "this also exists"
# when access to /#some_invalid_hash_fragment_for_malicious_attack
show404Error: ->
console.log "sorry, this page does not exist"
UPDATE:
I used constructor of Backbone.Controller to match current hash fragment and #routes.
class MyController extends Backbone.Controller
constructor: ->
super()
hash = window.location.hash.replace '#', ''
if hash
for k, v of #routes
if k is hash
return
#show404Error()
routes:
"method_a": "methodA"
"method_b": "methodB"
"*undefined": "show404Error"
# when access to /#method_a
methodA: ->
console.log "this page exists"
# when access to /#method_b
methodB: ->
console.log "this also exists"
# when access to /#some_invalid_hash_fragment_for_malicious_attack
show404Error: ->
console.log "sorry, this page does not exist"

Answer 1

The above works, but I'm not sure why you have to do what you do in the constructor. It may be slightly brittle, but we create a separate controller that we include in last. Its last so that the splat route is the last one to match:
NotFound = Backbone.Controller.extend({
routes: {
"*path" : "notFound"
},
notFound: function(path) {
var msg = "Unable to find path: " + path;
alert(msg);
}
});
new NotFound();
Using a more robust version of the above seems a cleaner approach to me.