feat(challenge36): add solution on trackby

apps/performance/ngfor-optimize/src/app/app.component.ts

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+import { Component, OnInit, inject } from '@angular/core';
+import { FormsModule } from '@angular/forms';
+import { MatFormFieldModule } from '@angular/material/form-field';
+import { MatInputModule } from '@angular/material/input';
+import { PersonService } from './list.service';
+import { PersonListComponent } from './person-list.component';
+
+@Component({
+  standalone: true,
+  imports: [
+    PersonListComponent,
+    FormsModule,
+    MatFormFieldModule,
+    MatInputModule,
+  ],
+  providers: [PersonService],
+  selector: 'app-root',
+  template: `
+    <h1 class="font-semibold text-center text-3xl" title="Title">
+      List of Persons
+    </h1>
+
+    <mat-form-field class="w-3/4">
+      <input
+        placeholder="Add one member to the list"
+        matInput
+        type="text"
+        [(ngModel)]="label"
+        (keydown)="handleKey($event)" />
+    </mat-form-field>
+
+    <app-person-list
+      class="max-w-2xl w-3/4"
+      [persons]="persons()"
+      (delete)="personService.deletePerson($event)"
+      (update)="personService.updatePerson($event)" />
+  `,
+  host: {
+    class: 'flex items-center flex-col gap-5',
+  },
+})
+export class AppComponent implements OnInit {
+  readonly personService = inject(PersonService);
+  readonly persons = this.personService.persons;
+
+  label = '';
+
+  ngOnInit(): void {
+    this.personService.loadPersons();
+  }
+
+  handleKey(event: any) {
+    if (event.keyCode === 13) {
+      this.personService.addPerson(this.label);
+      this.label = '';
+    }
+  }
+}

apps/performance/ngfor-optimize/src/app/app.config.ts

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+import { ApplicationConfig } from '@angular/core';
+import { provideAnimations } from '@angular/platform-browser/animations';
+
+export const appConfig: ApplicationConfig = {
+  providers: [provideAnimations()],
+};

apps/performance/ngfor-optimize/src/app/generateList.ts

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+import { randEmail, randFirstName } from '@ngneat/falso';
+import { Person } from './person.model';
+
+export function generateList() {
+  const arr: Person[] = [];
+
+  for (let i = 0; i < 50; i++) {
+    arr.push({
+      email: randEmail(),
+      name: randFirstName(),
+    });
+  }
+
+  return arr;
+}

apps/performance/ngfor-optimize/src/app/list.service.ts

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+import { Injectable, inject, signal } from '@angular/core';
+import { randEmail, randFirstName } from '@ngneat/falso';
+import { generateList } from './generateList';
+import { Person } from './person.model';
+
+@Injectable()
+export class PersonService {
+  private readonly fakeBackend = inject(FakeBackendService);
+  readonly persons = signal<Person[]>([]);
+
+  loadPersons() {
+    this.persons.set(generateList());
+  }
+
+  deletePerson(email: string) {
+    this.persons.set(
+      this.fakeBackend
+        .returnNewList(this.persons())
+        .filter((p) => p.email !== email)
+    );
+  }
+
+  updatePerson(email: string) {
+    this.persons.set(
+      this.fakeBackend
+        .returnNewList(this.persons())
+        .map((p) => (p.email === email ? { email, name: randFirstName() } : p))
+    );
+  }
+
+  addPerson(name: string) {
+    this.persons.set([
+      { email: randEmail(), name },
+      ...this.fakeBackend.returnNewList(this.persons()),
+    ]);
+  }
+}
+
+@Injectable({ providedIn: 'root' })
+export class FakeBackendService {
+  returnNewList = (input: Person[]): Person[] => [
+    ...input.map((i) => ({ ...i })),
+  ];
+}

apps/performance/ngfor-optimize/src/app/person-list.component.ts

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+import { Component, EventEmitter, Input, Output } from '@angular/core';
+
+import { CommonModule } from '@angular/common';
+import { Person } from './person.model';
+
+@Component({
+  selector: 'app-person-list',
+  standalone: true,
+  imports: [CommonModule],
+  template: `
+    <div
+      *ngFor="let person of persons"
+      class="flex justify-between items-center border-b">
+      <h3>{{ person.name }}</h3>
+      <div class="flex gap-10 py-1">
+        <button
+          class="border rounded-md p-2 bg-blue-500 text-white"
+          (click)="update.emit(person.email)">
+          UPDATE
+        </button>
+        <button
+          class="border rounded-md p-2 bg-red-500 text-white"
+          (click)="delete.emit(person.email)">
+          DELETE
+        </button>
+      </div>
+    </div>
+  `,
+  host: {
+    class: 'w-full flex flex-col',
+  },
+})
+export class PersonListComponent {
+  @Input() persons: Person[] = [];
+  @Output() delete = new EventEmitter<string>();
+  @Output() update = new EventEmitter<string>();
+}

apps/performance/ngfor-optimize/src/app/person.model.ts

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+export interface Person {
+  email: string;
+  name: string;
+}

apps/performance/ngfor-optimize/src/index.html

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+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <title>performance-ngfor-optimize</title>
+    <base href="/" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <link rel="icon" type="image/x-icon" href="favicon.ico" />
+  </head>
+  <body>
+    <app-root></app-root>
+  </body>
+</html>

apps/performance/ngfor-optimize/src/main.ts

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+import { bootstrapApplication } from '@angular/platform-browser';
+import { appConfig } from './app/app.config';
+import { AppComponent } from './app/app.component';
+
+bootstrapApplication(AppComponent, appConfig).catch((err) =>
+  console.error(err)
+);

apps/performance/ngfor-optimize/src/styles.scss

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+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+/* You can add global styles to this file, and also import other style files */

apps/performance/ngfor-optimize/src/test-setup.ts

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+import '@testing-library/jest-dom';
+import 'jest-preset-angular/setup-jest';