Angular7- Sort Select Dropdown options in Alphabetical Order

Question

I have a list of commodity items where i have to sort all IDM items in alphabetical order and below that DM items in alphabetical order, rite now my code displays like WRONG: order:but i want to display like Correct first IDM and next DM

**WRONG:**
    DM-Air
    DM-BELL
    DM-CEL
    IDM-AIR
    IDM-BELL
IDM-CELL

**CORRECT**
    IDM-AIR
    IDM-BELL
    IDM-CELL
    DM-Air
    DM-BELL
    DM-CEL

my code is

 this.supplier.getCommoditiesFamilyList().subscribe(
      (data: any) => {
        this.commoditiesFamilyList = data;
        this.commoditiesFamilyList.sort(this.commoditySortByName);
      },

this.supplier.getCommoditiesFamilyList(id).subscribe(
        data => {
          this.commoditiesFamilyList = data;
          this.commoditiesFamilyList.sort(this.commoditySortByName);
        },

 [![this.subscriberLevelId = id;
      this.supplier.getCommoditiesFamilyList(id).subscribe(
        data => {
          this.commoditiesFamilyList = data;
          this.commoditiesFamilyList.sort(this.commoditySortByName);
        },][1]][1]

public commoditySortByName(a, b) {
    if (a.name < b.name) {
      return -1;
    }
    if (a.name > b.name) {
      return 1;
    }
    return 0;
  }
}

Answer 1

You should just switch 1 and -1 in commoditySortByName function

Answer 2

I've written this for you, not knowing how you want to sort the part before the separation. My guess is reversed order?

  this.commoditiesFamilyList = this.commoditiesFamilyList
    .map(item => {
      var splitted: string[] = item.split('-');
      return {'pre': splitted[0], 'post': splitted[1]};
    })
    .sort(this.commoditySortByPre)
    .sort(this.commoditySortByPost)
    .map(item => item.pre + '-' + item.post);

  public commoditySortByPre(a, b) {
    if (a.pre < b.pre) {
      return 1;
    }
    if (a.pre > b.pre) {
      return -1;
    }
    return 0;
  }

  public commoditySortByPost(a, b) {
    if (a.name < b.name) {
      return -1;
    }
    if (a.name > b.name) {
      return 1;
    }
    return 0;
  }