toDictionary

toDictionary

Converts an array of objects to a dictionary { [key: string]: T }. Accepts an array T[] and a key of type string, number, or symbol. Returns a new dictionary and does not mutate the original array.

Immutability is explained in the immutability & serializable state concept.

Example

const creatures = [
  { id: 1, type: 'cat' },
  { id: 2, type: 'dog' },
  { id: 3, type: 'parrot' },
];

const creaturesDictionary = toDictionary(creatures, 'id');

// creaturesDictionary will be:
// {
//  1: {id: 1, type: 'cat'},
//  2: {id: 2, type: 'dog'},
//  3: {id: 3, type: 'parrot'}
// };

Example — with rxState()

import { Component } from '@angular/core';
import { Subject } from 'rxjs';
import { rxState } from '@rx-angular/state';
import { toDictionary } from '@rx-angular/cdk/transformations';

@Component({
  /* ... */
})
export class ListComponent {
  readonly convertToDictionary$ = new Subject<void>();

  private readonly state = rxState<ComponentState>(({ connect }) => {
    connect('creaturesDictionary', this.convertToDictionary$, ({ creatures }) => toDictionary(creatures, 'id'));
  });

  readonly creaturesDictionary = this.state.signal('creaturesDictionary');

  // Imperative alternative
  convertToDictionary(): void {
    this.state.set({
      creaturesDictionary: toDictionary(this.state.get('creatures'), 'id'),
    });
  }
}

Example — signals-first

import { signal, computed } from '@angular/core';
import { toDictionary } from '@rx-angular/cdk/transformations';

const creatures = signal<Creature[]>([]);

const creaturesDictionary = computed(() => toDictionary(creatures(), 'id'));

Edge cases

toDictionary([] as any, 'nonExistingKey') > {};
toDictionary(items, 'nonExistingKey') > {};
toDictionary(items, 'nonPrimitiveKey' as any) > {};
toDictionary(items, null as any) > {};
toDictionary(nonObject as any, '') > {};
toDictionary(null as any, '') > null;
toDictionary(undefined as any, '') > undefined;

Signature

function toDictionary<T extends object>(source: T[], key: OnlyKeysOfSpecificType<T, number> | OnlyKeysOfSpecificType<T, string> | OnlyKeysOfSpecificType<T, symbol>): { [key: string]: T };

Parameters

source

typeof: T[]

key

typeof: | OnlyKeysOfSpecificType<T, number>

 | OnlyKeysOfSpecificType<T, string>
 | OnlyKeysOfSpecificType<T, symbol>