How do stop adding duplicate chips in an autocomplete component?

Question

How can I stop adding duplicate values in the list using Angular Material chips? So, for example, I want to add Apple only one in the fruits list, and when I add Lemon also I want to add only one. Now I can add multiple times. And when I close the chip I would like to be able to add it again. I would appreciate any help. Thanks!

import {COMMA, ENTER} from '@angular/cdk/keycodes';
import {Component, ElementRef, ViewChild} from '@angular/core';
import {FormControl} from '@angular/forms';
import {MatAutocompleteSelectedEvent, MatChipInputEvent} from '@angular/material';
import {Observable} from 'rxjs';
import {map, startWith} from 'rxjs/operators';

/**
 * @title Chips Autocomplete
 */
@Component({
  selector: 'chips-autocomplete-example',
  templateUrl: 'chips-autocomplete-example.html',
  styleUrls: ['chips-autocomplete-example.css']
})
export class ChipsAutocompleteExample {
  visible: boolean = true;
  selectable: boolean = true;
  removable: boolean = true;
  addOnBlur: boolean = false;

  separatorKeysCodes = [ENTER, COMMA];

  fruitCtrl = new FormControl();

  filteredFruits: Observable<any[]>;

  fruits = [
    'Lemon',
  ];

  allFruits = [
    'Apple',
    'Lemon',
    'Lime',
    'Orange',
    'Strawberry'
  ];

  @ViewChild('fruitInput') fruitInput: ElementRef;

  constructor() {
    this.filteredFruits = this.fruitCtrl.valueChanges.pipe(
        startWith(null),
        map((fruit: string | null) => fruit ? this.filter(fruit) : this.allFruits.slice()));
  }

  add(event: MatChipInputEvent): void {
    const input = event.input;
    const value = event.value;

    // Add our fruit
    if ((value || '').trim()) {
      this.fruits.push(value.trim());
    }

    // Reset the input value
    if (input) {
      input.value = '';
    }

    this.fruitCtrl.setValue(null);
  }

  remove(fruit: any): void {
    const index = this.fruits.indexOf(fruit);

    if (index >= 0) {
      this.fruits.splice(index, 1);
    }
  }

  filter(name: string) {
    return this.allFruits.filter(fruit =>
        fruit.toLowerCase().indexOf(name.toLowerCase()) === 0);
  }

  selected(event: MatAutocompleteSelectedEvent): void {
    this.fruits.push(event.option.viewValue);
    this.fruitInput.nativeElement.value = '';
    this.fruitCtrl.setValue(null);
  }
}


/**  Copyright 2018 Google Inc. All Rights Reserved.
    Use of this source code is governed by an MIT-style license that
    can be found in the LICENSE file at http://angular.io/license */

<mat-form-field class="demo-chip-list">
  <mat-chip-list #chipList>
    <mat-chip
      *ngFor="let fruit of fruits"
      [selectable]="selectable"
      [removable]="removable"
      (removed)="remove(fruit)">
      {{fruit}}
      <mat-icon matChipRemove *ngIf="removable">cancel</mat-icon>
    </mat-chip>
    <input
      placeholder="New fruit..."
      #fruitInput
      [formControl]="fruitCtrl"
      [matAutocomplete]="auto"
      [matChipInputFor]="chipList"
      [matChipInputSeparatorKeyCodes]="separatorKeysCodes"
      [matChipInputAddOnBlur]="addOnBlur"
      (matChipInputTokenEnd)="add($event)"
    />
  </mat-chip-list>
  <mat-autocomplete #auto="matAutocomplete" (optionSelected)="selected($event)">
    <mat-option *ngFor="let fruit of filteredFruits | async" [value]="fruit">
      {{ fruit }}
    </mat-option>
  </mat-autocomplete>
</mat-form-field>

<!-- Copyright 2018 Google Inc. All Rights Reserved.
    Use of this source code is governed by an MIT-style license that
    can be found in the LICENSE file at http://angular.io/license -->

Answer 1

You can check if the item is already present in the array and then add.

Try like this:

// Add our fruit
if ((value || '').trim()) {
  if(!this.fruits.includes(value.trim())) {
    this.fruits.push(value.trim());
  }
}

or

// Add our fruit
if ((value || '').trim()) {
    let index =   this.fruits.indexOf(value.trim())
    if(index == -1)
      this.fruits.push(value.trim());
}

Answer 2

To remove it from the list when the element is already added remove it from the option like this:

<mat-option *ngIf="!fruits.includes(fruit)" [value]="fruit">
  {{fruit}}
</mat-option>