Removing empty options from a select dropdown in Angular 9

In the process of working with Angular 9, I am currently in the process of constructing a dropdown menu that contains various options. However, I have encountered an issue where there is a blank option displayed when the page initially loads. How can I eliminate this blank option?

Below is the current code snippet that I am using:

<form #f="ngForm">
  <select aria-labelledby="dropdownMenuButton" [(ngModel)]="selectedValue" (change)="hideShowElements($event.target.value)">
    <option [ngValue]="null">Show All</option>
    <option *ngFor="let item of response.results | filterUnique;" [ngValue]="item.section">{{item.section}}</option>
  </select>
</form>

I would appreciate any assistance with resolving this matter!

typescriptangular9

Answer №1

When the initial item selected in your template is set to null, it's important to also assign null to the value bound to the field's ngModel.

  • It's crucial to note that using undefined will result in an empty value in the select element.
  • If you set a value that isn't one of the available options, the displayed option will be blank. For example, if the range is 1 to 5 but the current value of selectedValue is 6.

app.component.ts

export class AppComponent  {
  selectedValue: number = null;
  selectedValue2: number;
}

app.html

<h3>Example with an assignment to null<h3>
<select aria-labelledby="dropdownMenuButton" [(ngModel)]="selectedValue">
  <option [ngValue]="null">Show All</option>
  <option [ngValue]="1">One</option>
  <option [ngValue]="2">Two</option>
</select>

<h3>Example with no assignment to null<h3>
<select aria-labelledby="dropdownMenuButton" [(ngModel)]="selectedValue2">
  <option [ngValue]="null">Show All</option>
  <option [ngValue]="1">One</option>
  <option [ngValue]="2">Two</option>
</select>

For a demonstration, check out this functioning stackblitz example.

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