How to get index of selected option in Angular

Question

I am trying to get the selected option index of a select using Angular. I am using Angular (4) and Ionic 3.

My template looks like below:

<ion-select [(ngModel)]="obj.city">
   <ion-option *ngFor="let city of cities; let i = index;" 
                [value]="city"  [selected]="i == 0">
                {{city.name}}
   </ion-option>
</ion-select>

I want the index of selected city to be accessed in Component code. Lets say, I want that index to be assigned to a variable selectedCityIndex in component.

My current code is pre selecting the first option as default. Solution should not break this functionality.

I am searching for a solution which do not include interating the array (i.e. no loop in JavaScript part). It should not use "indexOf" method or document's methods like "document.getElementById". I am not using jQuery.

Answer 1

If you want index in the component class file, please check this plnkr https://plnkr.co/edit/9Z7jjeSW7fmTUR7SbqNk?p=preview

//our root app component
import {Component, NgModule} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser'
import { FormsModule } from '@angular/forms';

@Component({
  selector: 'my-app',
  template: `
    <h2>Select demo</h2>
    <select (change)="onChange($event.target.value)" >
      <option *ngFor="let c of cities;let i = index" [value]="i"> {{c.name}} </option>
    </select>
  `
})

class App {

  public value:integer;
  cities = [{'name': 'Pune'}, {'name': 'Mumbai'}, {'name': 'Nagar'}];
  selectedCity = this.cities[1];

  constructor() {
    this.value = 0;
  }
  onChange(cityindex) {
    console.log(cityindex);
    alert(cityindex);
  }

}


@NgModule({
  imports: [ BrowserModule, FormsModule ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

Hope this helps.

Answer 2

After wasting 3 hours, I found a single line java script solution.

you can use event.target["selectedIndex"] - 1 to get the selectedIndex of select.

Example:

<select class="form-control selectpicker" #Code name="Code" [(ngModel)]="model.Code" (change)="searchWithCode($event)" >
    <option value="" selected="selected">--Please select--</option>
    <option *ngFor="let x of Codes" [value]="x.Code" [selected]="x.Code == model.Code">{{x.Name}}</option>
</select>



searchWithCode(event:Event) : void {
    let index:number = use event.target["selectedIndex"] - 1;
}

Reference: https://github.com/angular/angular/issues/18842#issuecomment-324399823