How do you add dynamic queryParams to Backbone pageableCollection before syc - backbone.js

Question

I am new to Backbone and I am trying to add extra parameter offset to queryParams before fetch sync occurs as the API does not support page, this is what I have tried to intercept the sync before sending options but it doesn't work, does anyone know how to achieve this?
Backbone.PageableCollection.extend({
model: Entities.Role,
url: function () {
return App.API + 'role';
},
mode: "server",
state: {
pageSize: 15,
order: 1,
firstPage: 1,
currentPage: 1
},
// You can remap the query parameters from `state` keys from
// the default to those your server supports
queryParams: {
offset: 0,
totalPages: null,
totalRecords: null,
sortKey: "sort",
pageSize: "max"
},
sync: function(method, model, options){
var defer = $.Deferred();
options.beforeSend=function(xhr) {
options.data.offset=(parseInt(model.state.currentPage) - 1) * model.state.pageSize;
model.queryParams.offset=(parseInt(model.state.currentPage) - 1) * model.state.pageSize;
defer.resolve(method, model, options);
}
return defer.promise(Backbone.sync(method, model, options));
}
});

Answer 1

solved:
you dont need to use defer - just works with:
sync: function(method, model, options){
options.data.offset=(parseInt(model.state.currentPage) - 1) * model.state.pageSize;
model.queryParams.offset=(parseInt(model.state.currentPage) - 1) * model.state.pageSize;
return Backbone.sync(method, model, options);
}