Angular 2+ - check if Pipe returns an empty subset of original list

Question

I have a list of strings that I want to iterate through, but I want to be able to filter them using a search term. Like this:

        
                      

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Answer 1

This is the cleanest solution I've been able to produce.

@Pipe({
  name: 'search'
})
export class SearchPipe {

  transform(value, searchTerm) {
    let result = ...
    if(result.length === 0) {
      return [undefined];
    }
    return result;
  }
}

By returning [undefined], checks in the DOM are much cleaner and easier to read.

<ng-container *ngFor="let item of list | search: searchTerm">
  <div *ngIf="!item">"No matches"</div>
  <div *ngIf="item">{{ item }}</div>
</ng-container>