Ember.js serializer TypeError: payload.map is not a function

I am new to Ember and I am using a JSONSerializer to change my JSON. This is my code

import JSONSerializer from 'ember-data/serializers/json';

export default JSONSerializer.extend({
 normalizeResponse(store, primaryModelClass, payload, id, requestType) {

 var listOptions = payload.clients;


 for(i = 0; i < listOptions.length; i++) {
  //we do some operations and we end up with foo
 }

 newData = foo;

 for(i = 0; i < payload.clients.length; i++) {
    payload.clients[i].NAME = newData[i].text; 
    payload.clients[i].id = newData[i].value; 
 }

 return this._super(...arguments);

}

And in the return I get this error:

ember.debug.js:27431 Error while processing route: index payload.map is not a function TypeError: payload.map is not a function

My version of Ember is 2.4.3 .

So gurus of Ember what is going wrong with my code?, my return is exactly like the ones from the documentation and I am getting a bit desperate. http://ift.tt/1VRZQKi .

Thank you very much.