Angular 2 Dropdown Options Default Value

Question

In Angular 1 I could select the default option for a drop down box using the following:

<select 
    data-ng-model="carSelection"
    data-ng-options = "x.make for x in cars" data-ng-selected="$first">
</select>

In Angular 2 I have:

<select class="form-control" [(ngModel)]="selectedWorkout" (ngModelChange)="updateWorkout($event)">
    <option *ngFor="#workout of workouts">{{workout.name}}</option>
</select>

How could I select a default option given my option data is:

[{name: 'arm'}, {name: 'back'}, {name:'leg'}] and my value I to default on on is back?

Answer 1

Add on to @Matthijs 's answer, please make sure your select element has a name attribute and its name is unique in your html template. Angular 2 is using input name to update changes. Thus, if there are duplicated names or there is no name attached to input element, the binding will fail.

Answer 2

Step: 1 Create Properties declare class

export class Task {
    title: string;
    priority: Array<any>;
    comment: string;

    constructor() {
        this.title      = '';
        this.priority   = [];
        this.comment    = '';
     }
}

Stem: 2 Your Component Class

import { Task } from './task';

export class TaskComponent implements OnInit {
  priorityList: Array<any> = [
    { value: 0, label: '✪' },
    { value: 1, label: '★' },
    { value: 2, label: '★★' },
    { value: 3, label: '★★★' },
    { value: 4, label: '★★★★' },
    { value: 5, label: '★★★★★' }
  ];
  taskModel: Task           = new Task();

  constructor(private taskService: TaskService) { }
  ngOnInit() {
    this.taskModel.priority     = [3]; // index number
  }
}

Step: 3 View File .html

<select class="form-control" name="priority" [(ngModel)]="taskModel.priority"  required>
    <option *ngFor="let list of priorityList" [value]="list.value">
      {{list.label}}
    </option>
</select>

Output:

Answer 3

According to https://angular.io/api/forms/SelectControlValueAccessor you just need the following:

theView.html:

<select [compareWith]="compareFn"  [(ngModel)]="selectedCountries">
    <option *ngFor="let country of countries" [ngValue]="country">
        {{country.name}}
    </option>
</select>

theComponent.ts

import { SelectControlValueAccessor } from '@angular/forms';
    compareFn(c1: Country, c2: Country): boolean {
    return c1 && c2 ? c1.id === c2.id : c1 === c2;
}

Answer 4

Add binding property selected, but make sure to make it null, for other fields e.g:

<option *ngFor="#workout of workouts" [selected]="workout.name =='back' ? true: null">{{workout.name}}</option>

Now it will work

Answer 5

You can Use that [ngModel] instead of [(ngModel)]and it is Ok

<select class="form-control" **[ngModel]="selectedWorkout"** (ngModelChange)="updateWorkout($event)">
   <option *ngFor="#workout of workouts">{{workout.name}}</option>
</select>

Answer 6

You can do as above:

<select class="form-control" 
        [(ngModel)]="selectedWorkout" 
        (ngModelChange)="updateWorkout($event)">
    <option *ngFor="#workout of workouts;
                    let itemIndex = index"
            [attr.selected]="itemIndex == 0">
    {{workout.name}}
    </option>
</select>

In above code as you can see, selected attribute of the repeating option is set on checking index of the repeating loop of list. [attr.< html attribute name >] is used for setting html attribute in angular2.

Another approach will be setting model value in typescript file as :

this.selectedWorkout = this.workouts.length > 0
                       ? this.workouts[0].name
                       : 'No data found';//'arm'