Arrays vs Objects.

Array

    this.addToResponses = function(responses, interventionId, questiongroupId, questiongroupInstanceId, questionId, response) {
      if (!responses.questiongroups) {
        responses.interventionId = interventionId
        responses.questiongroups = new Array()
      }
      if(!responses.questiongroups[????????]) {
        responses.questiongroups.push({Id: questiongroupId, questiongroupInstances:{}})
      }
      if (!responses.questiongroups[????????].questiongroupInstances[questiongroupInstanceId]){
        responses.questiongroups[????????].questiongroupInstances.push({Id: questiongroupInstanceId, questions:{}})
      }
      if (!responses.questiongroups[????????].questiongroupInstances[????????].questions[????????]){
        responses.questiongroups[????????].questiongroupInstances[????????].questions.push({Id:questionId, response: response})
      }
    }

Object

    this.addToResponses = function(responses, interventionId, questiongroupId, questiongroupInstanceId, questionId, response) {
      if (!responses.questiongroups) {
        responses.interventionId = interventionId
        responses.questiongroups = {}
      }
      if(!responses.questiongroups[questiongroupId]) {
        responses.questiongroups[questiongroupId] = {Id: questiongroupId, questiongroupInstances:{}}
      }
      if (!responses.questiongroups[questiongroupId].questiongroupInstances[questiongroupInstanceId]){
        responses.questiongroups[questiongroupId].questiongroupInstances[questiongroupInstanceId] = {Id: questiongroupInstanceId, questions:{}}
      }
      if (!responses.questiongroups[questiongroupId].questiongroupInstances[questiongroupInstanceId].questions[questionId]){
        responses.questiongroups[questiongroupId].questiongroupInstances[questiongroupInstanceId].questions[questionId] = {Id:questionId, response: response}
      }
    }