Is it possible to prevent changing of router by clicking back button? - backbone.js

Question

I'am building single page using BackboneJS and I need to prevent router executing on back button in a browser. To be exact I need to show confirmation custom popup with the text "Do you really want exit room? [yes|no]". So if user clicks yes then default actions should happens but if no then user should stay in the current screen.
I use Backbone.router with pushState: true. Does Backbonejs provide something like before router event to be possible prevent router handling or how could I archive it?

Answer 1

I'm not sure if this is still an issue, but this is how I would get around it. It may not be the best way, but could be a step in the right direction.
Backbone.History.prototype.loadUrl = function (fragment, options) {
var result = true;
if (fragment === void (0) && options === void (0) && this.confirmationDisplay !== void(0))
{
result = confirm('Are you sure you want to leave this room?');
}
var opts = options;
fragment = Backbone.history.fragment = Backbone.history.getFragment(fragment);
if (result) {
this.confirmationDisplay = true;
return _.any(Backbone.history.handlers, function (handler) {
if (handler.route.test(fragment)) {
//We just pass in the options
handler.callback(fragment, opts);
return true;
}
});
}
return this;
}
Essentially checking if we have a fragment and options, if not, we can assume the app just started, or the user clicked the back button.

Answer 2

Backbone router has an execute method which is called for every route change, we can return false to prevent the current transition. The code will probably look like below :
With an asynchronous popup (untested code, but should work)
Backbone.Route.extend({
execute: function(callback,args){
if(this.lastRoute === 'room'){
showPopup().done(function(){
callback & callback.apply(this,args);
}).fail(function(){
Backbone.history.navigate('room/486',{trigger:false});
});
}else{
callback && callback.apply(this,args);
}
},
showPopup: function(){
var html = "<<div><p>Do you really want to exit</p><button id='yes'>Yes</button><button id='no'>No</button></div>"
var promise = $.Deferred();
$('body').append(html);
$(document).on('click','button#yes',function(){
promise.resolve();
});
$(document).on('click','button#no',function(){
promise.reject();
});
return promise;
}
});
With synchronous confirm popup
Backbone.Route.extend({
execute: function(callback,args){
if(this.lastRoute === 'room'){
var conf = confirm("Do you really want to exit the room ?");
if(!conf){
//Change the route back to room
Backbone.history.navigate('room/486',{trigger:false});
return false;
}
};
callback && callback.apply(this,args);
}
});
References:
http://backbonejs.org/#Router-execute