How to check whether the selected option already registered or selected in ionic 2


lets say I have admin that wants to register some courses for a particular student , I have followed a way in order to list check boxes that can be multiply selected.

here is the code:

    constructor(public schooAppUsers: SchooAppUsers) { 
    schoolAppUsers.loadAllCourses().subscribe(response => {
    this.response = response;

    // Action sheet code that displays a button and calls {


   let options = this.response;
   let select = {
   title: 'My Select',
   inputs: [],
   multiple: true,
   buttons: [{ 
   text: 'ok',
    handler: data => {

 for (var i=0; i<options.length; i++)
     select.inputs.push({name: 'myInputs', label: options[i].CourseName,  value: options[i].CourseID, type: 'checkbox'});
   let newAlert = this.alertCtrl.create(select);

Issue[1]: the service loadAllCourse(), lists all courses in the data base, however, the student might already be registered to some courses, how do I exclude those courses/options from displaying.

Issue[2]: how to store the data back to the server , this is what I’m doing but it displays the alert in every loop and I’m failing to find a work around this. this is inside handler: data {}

  for (let course of data){
    this.schoolAppUsers.insertStudentCourse(this.UserID, course).subscribe(res => {
      let alert = this.alertCtrl.create({
        message: res[0].message,
        buttons: [{
        text: 'Ok',
        handler: () =>{
          let navTransition = alert.dismiss();
           navTransition.then(() => {
        return false;