How to implement select all in angular material drop down angular 5

Question

I am using mat-select to display drop down, I need select all functionality in angular drop down.

Below is my html

<mat-select formControlName="myControl" multiple (ngModelChange)="resetSelect($event, 'myControl')">
    <mat-option>Select All</mat-option>
    <mat-option [value]="1">Option 1</mat-option>
    <mat-option [value]="2">Option 2</mat-option>
    <mat-option [value]="3">Option 3</mat-option>
</mat-select>

Here is my ts code

/**
 * click handler that resets a multiple select
 * @param {Array} $event current value of the field
 * @param {string} field name of the formControl in the formGroup
 */
protected resetSelect($event: string[], field: string) {
    // when resetting the value, this method gets called again, so stop recursion if we have no values
    if ($event.length === 0) {
        return;
    }
    // first option (with no value) has been clicked
    if ($event[0] === undefined) {
        // reset the formControl value
        this.myFormGroup.get(field).setValue([]);
    }
}

Some how its not working properly, kindly help or let me any better way to do this.

Solution 1

Use click event try this

<mat-form-field>
  <mat-select placeholder="Toppings" [formControl]="toppings" multiple>
    <mat-option [value]="1" (click)="selectAll(ev)"   
    #ev
     >SelectAll</mat-option>
    <mat-option *ngFor="let topping of toppingList" [value]="topping">{{topping}}</mat-option>
  </mat-select>
</mat-form-field>

}

Typescript:

selectAll(ev) {
    if(ev._selected) {
        this.toppings.setValue(['Extra cheese', 'Mushroom', 'Onion', 'Pepperoni', 'Sausage', 'Tomato']);
        ev._selected=true;
    }
    if(ev._selected==false) {
      this.toppings.setValue([]);
    }
}

Example:https://stackblitz.com/edit/angular-czmxfp

Solution 2

I extended Angular Material's MatSelect to include following features:

• Search
• Grouping
• Select All
• Select all options under a group

Working example can be found here on StackBlitz and complete repository can be found here on GitHub

Following is the code snippet of "Select All" implementation

HTML

<button *ngIf="isGroup && values.length" mat-icon-button (click)="toggleGroup()">
  <mat-icon>
    {{ isCollapsed ? 'chevron_right' : 'expand_more' }}
  </mat-icon>
</button>

<ng-container *ngIf="values.length" [ngSwitch]="isMultiple">
  <mat-checkbox *ngSwitchCase="true" disableRipple matRipple class="mat-option" color="primary"
    [ngClass]="{ 'mat-selected': isIndeterminate() || isChecked() }" [indeterminate]="isIndeterminate()"
    [checked]="isChecked()" (click)="$event.stopPropagation()" (change)="toggleSelection($event)">
    {{text}}
  </mat-checkbox>
  <span *ngSwitchDefault>
    {{text}}
  </span>
</ng-container>

TS

import { Component, Input, ViewEncapsulation, OnChanges, SimpleChanges, ChangeDetectionStrategy, ChangeDetectorRef, OnInit, OnDestroy } from '@angular/core';
import { FormControl } from '@angular/forms';
import { MatCheckboxChange } from '@angular/material';
import { Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

@Component({
  // tslint:disable-next-line:component-selector
  selector: 'mat-select-check',
  templateUrl: './mat-select-check.component.html',
  styleUrls: ['./mat-select-check.component.css'],
  encapsulation: ViewEncapsulation.None,
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class MatSelectCheckComponent implements OnChanges, OnInit, OnDestroy {
  @Input() selectControl: FormControl;
  @Input() values = [];
  @Input() text = 'Select All';
  @Input() isGroup = false;
  @Input() groupData: any;
  @Input() dataKey = 'Key';
  @Input() isMultiple?: boolean;

  private _onDestroy = new Subject<void>();
  isCollapsed = false;

  constructor(private changeDetectorRef: ChangeDetectorRef) { }

  ngOnChanges(changes: SimpleChanges) {
    if (changes && changes.values && changes.values.currentValue && changes.values.currentValue.length) {
      this.values = changes.values.currentValue.map(z => z[this.dataKey]);
    }

    setTimeout(() => {
      this.changeDetectorRef.detectChanges();
    });
  }

  ngOnInit() {
    if (this.selectControl) {
      this.selectControl.valueChanges
      .pipe(takeUntil(this._onDestroy))
      .subscribe(value => setTimeout(() => {
        this.changeDetectorRef.detectChanges();
      }));
    }
  }

  ngOnDestroy() {
    this._onDestroy.next();
    this._onDestroy.complete();
  }

  isChecked(): boolean {
    const hasValues = this.selectControl.value && this.values.length && this.selectControl.value.length;
    if (hasValues) {
      const length = this.selectControl.value.filter(x => this.values.includes(x)).length;
      return length > 0 && length === this.values.length;
    }
    return false;
  }

  isIndeterminate(): boolean {
    const hasValues = this.selectControl.value && this.values.length && this.selectControl.value.length;
    if (hasValues) {
      const length = this.selectControl.value.filter(x => this.values.includes(x)).length;
      return length > 0 && length < this.values.length;
    }
    return false;
  }

  toggleSelection(change: MatCheckboxChange): void {
    if (change.checked) {
      const newValue = this.selectControl.value ? [...this.selectControl.value, ...this.values] : [...this.values];
      this.selectControl.setValue(Array.from(new Set(newValue)));
    } else {
      this.selectControl.setValue(this.selectControl.value.filter(x => !this.values.includes(x)));
    }
  }

  toggleGroup() {
    this.isCollapsed = !this.isCollapsed;
    this.groupData[this.groupData.findIndex(x => x.key === this.text)].isVisible = !this.isCollapsed;
  }
}

Comments

[kunal]

Thanks for the response, how to deselect all on again click

[Chellappan வ]

can you check the stack blitz example use template variable to manually uncheck the check box

[Jonathan Anctil]

Excellent sample. Question: how do you check by default the select all option?

[Chellappan வ]

Hi @JonathanAnctil Since In my example I am using reactive form we can call setValue and pass all the value to select all toppings.setValue([1,.....])