3 - Archivos y carpetas básicas de un proyecto en Angular

Vimos en el concepto anterior que para crear un proyecto en Angular utilizamos la herramienta Angular CLI y desde la línea de comandos escribimos:

ng new proyecto001

No haremos por el momento un estudio exhaustivo de todos los archivos y carpetas que se crean (más 55000 archivos y 4700 carpetas en la versión de Angular 9.x), sino de aquellas que se requieren modificar según el concepto que estemos estudiando.

En Angular la pieza fundamental es la 'COMPONENTE'. Debemos pensar siempre que una aplicación se construye a base de un conjunto de componentes (por ejemplo pueden ser componentes: un menú, lista de usuarios, login, tabla de datos, calendario, formulario de búsqueda etc.)

Angular CLI nos crea una única componente llamada 'AppComponent' que se distribuye en 4 archivos:

app.component.ts
app.component.html
app.component.css
app.component.spec.ts

Todos estos archivos se localizan en la carpeta 'app' y esta carpeta se encuentra dentro de la carpeta 'src':

archivos y carpetas Angular

En Angular se programa utilizando el lenguaje TypeScript que vamos a ir aprendiéndolo a lo largo del curso. El archivo donde se declara la clase AppComponent es 'app.component.ts':

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'proyecto001';
}

La Clase AppComponent define un atributo llamado 'title' y lo inicializa con el string 'proyecto001' que coincide con el nombre del proyecto que creamos:

  title = 'proyecto001';

Dijimos anteriormente que la clase completa se distribuye en otros archivos y podemos ver que mediante la función decoradora @Component le indicamos los otros archivos que pertenecen a esta componente:

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})

El archivo 'app.component.html' tiene la parte visual de nuestra componente 'AppComponent' y está constituido mayormente por código HTML (cada vez que realicemos un proyecto a este código lo borraremos para resolver nuestro problema):

<!-- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -->
<!-- * * * * * * * * * * * The content below * * * * * * * * * * * -->
<!-- * * * * * * * * * * is only a placeholder * * * * * * * * * * -->
<!-- * * * * * * * * * * and can be replaced. * * * * * * * * * * * -->
<!-- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -->
<!-- * * * * * * * * * Delete the template below * * * * * * * * * * -->
<!-- * * * * * * * to get started with your project! * * * * * * * * -->
<!-- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * -->

<style>
  :host {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    font-size: 14px;
    color: #333;
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
  }

  h1,
  h2,
  h3,
  h4,
  h5,
  h6 {
    margin: 8px 0;
  }

  p {
    margin: 0;
  }

  .spacer {
    flex: 1;
  }

  .toolbar {
    height: 60px;
    margin: -8px;
    display: flex;
    align-items: center;
    background-color: #1976d2;
    color: white;
    font-weight: 600;
  }

  .toolbar img {
    margin: 0 16px;
  }

  .toolbar #twitter-logo {
    height: 40px;
    margin: 0 16px;
  }

  .toolbar #twitter-logo:hover {
    opacity: 0.8;
  }

  .content {
    display: flex;
    margin: 32px auto;
    padding: 0 16px;
    max-width: 960px;
    flex-direction: column;
    align-items: center;
  }

  svg.material-icons {
    height: 24px;
    width: auto;
  }

  svg.material-icons:not(:last-child) {
    margin-right: 8px;
  }

  .card svg.material-icons path {
    fill: #888;
  }

  .card-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    margin-top: 16px;
  }

  .card {
    border-radius: 4px;
    border: 1px solid #eee;
    background-color: #fafafa;
    height: 40px;
    width: 200px;
    margin: 0 8px 16px;
    padding: 16px;
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    transition: all 0.2s ease-in-out;
    line-height: 24px;
  }

  .card-container .card:not(:last-child) {
    margin-right: 0;
  }

  .card.card-small {
    height: 16px;
    width: 168px;
  }

  .card-container .card:not(.highlight-card) {
    cursor: pointer;
  }

  .card-container .card:not(.highlight-card):hover {
    transform: translateY(-3px);
    box-shadow: 0 4px 17px rgba(black, 0.35);
  }

  .card-container .card:not(.highlight-card):hover .material-icons path {
    fill: rgb(105, 103, 103);
  }

  .card.highlight-card {
    background-color: #1976d2;
    color: white;
    font-weight: 600;
    border: none;
    width: auto;
    min-width: 30%;
    position: relative;
  }

  .card.card.highlight-card span {
    margin-left: 60px;
  }

  svg#rocket {
    width: 80px;
    position: absolute;
    left: -10px;
    top: -24px;
  }

  svg#rocket-smoke {
    height: calc(100vh - 95px);
    position: absolute;
    top: 10px;
    right: 180px;
    z-index: -10;
  }

  a,
  a:visited,
  a:hover {
    color: #1976d2;
    text-decoration: none;
  }

  a:hover {
    color: #125699;
  }

  .terminal {
    position: relative;
    width: 80%;
    max-width: 600px;
    border-radius: 6px;
    padding-top: 45px;
    margin-top: 8px;
    overflow: hidden;
    background-color: rgb(15, 15, 16);
  }

  .terminal::before {
    content: "\2022 \2022 \2022";
    position: absolute;
    top: 0;
    left: 0;
    height: 4px;
    background: rgb(58, 58, 58);
    color: #c2c3c4;
    width: 100%;
    font-size: 2rem;
    line-height: 0;
    padding: 14px 0;
    text-indent: 4px;
  }

  .terminal pre {
    font-family: SFMono-Regular,Consolas,Liberation Mono,Menlo,monospace;
    color: white;
    padding: 0 1rem 1rem;
    margin: 0;
  }

  .circle-link {
    height: 40px;
    width: 40px;
    border-radius: 40px;
    margin: 8px;
    background-color: white;
    border: 1px solid #eeeeee;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);
    transition: 1s ease-out;
  }

  .circle-link:hover {
    transform: translateY(-0.25rem);
    box-shadow: 0px 3px 15px rgba(0, 0, 0, 0.2);
  }

  footer {
    margin-top: 8px;
    display: flex;
    align-items: center;
    line-height: 20px;
  }

  footer a {
    display: flex;
    align-items: center;
  }

  .github-star-badge {
    color: #24292e;
    display: flex;
    align-items: center;
    font-size: 12px;
    padding: 3px 10px;
    border: 1px solid rgba(27,31,35,.2);
    border-radius: 3px;
    background-image: linear-gradient(-180deg,#fafbfc,#eff3f6 90%);
    margin-left: 4px;
    font-weight: 600;
    font-family: -apple-system,BlinkMacSystemFont,Segoe UI,Helvetica,Arial,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol;
  }

  .github-star-badge:hover {
    background-image: linear-gradient(-180deg,#f0f3f6,#e6ebf1 90%);
    border-color: rgba(27,31,35,.35);
    background-position: -.5em;
  }

  .github-star-badge .material-icons {
    height: 16px;
    width: 16px;
    margin-right: 4px;
  }

  svg#clouds {
    position: fixed;
    bottom: -160px;
    left: -230px;
    z-index: -10;
    width: 1920px;
  }


  /* Responsive Styles */
  @media screen and (max-width: 767px) {

    .card-container > *:not(.circle-link) ,
    .terminal {
      width: 100%;
    }

    .card:not(.highlight-card) {
      height: 16px;
      margin: 8px 0;
    }

    .card.highlight-card span {
      margin-left: 72px;
    }

    svg#rocket-smoke {
      right: 120px;
      transform: rotate(-5deg);
    }
  }

  @media screen and (max-width: 575px) {
    svg#rocket-smoke {
      display: none;
      visibility: hidden;
    }
  }
</style>

<!-- Toolbar -->
<div class="toolbar" role="banner">
  <img
    width="40"
    alt="Angular Logo"
    src="data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHZpZXdCb3g9IjAgMCAyNTAgMjUwIj4KICAgIDxwYXRoIGZpbGw9IiNERDAwMzEiIGQ9Ik0xMjUgMzBMMzEuOSA2My4ybDE0LjIgMTIzLjFMMTI1IDIzMGw3OC45LTQzLjcgMTQuMi0xMjMuMXoiIC8+CiAgICA8cGF0aCBmaWxsPSIjQzMwMDJGIiBkPSJNMTI1IDMwdjIyLjItLjFWMjMwbDc4LjktNDMuNyAxNC4yLTEyMy4xTDEyNSAzMHoiIC8+CiAgICA8cGF0aCAgZmlsbD0iI0ZGRkZGRiIgZD0iTTEyNSA1Mi4xTDY2LjggMTgyLjZoMjEuN2wxMS43LTI5LjJoNDkuNGwxMS43IDI5LjJIMTgzTDEyNSA1Mi4xem0xNyA4My4zaC0zNGwxNy00MC45IDE3IDQwLjl6IiAvPgogIDwvc3ZnPg=="
  />
  <span>Welcome</span>
    <div class="spacer"></div>
    <a aria-label="Angular on twitter" target="_blank" rel="noopener" href="https://twitter.com/angular" title="Twitter">
      <svg id="twitter-logo" height="24" data-name="Logo" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 400 400">
        <rect width="400" height="400" fill="none"/>
        <path d="M153.62,301.59c94.34,0,145.94-78.16,145.94-145.94,0-2.22,0-4.43-.15-6.63A104.36,104.36,0,0,0,325,122.47a102.38,102.38,0,0,1-29.46,8.07,51.47,51.47,0,0,0,22.55-28.37,102.79,102.79,0,0,1-32.57,12.45,51.34,51.34,0,0,0-87.41,46.78A145.62,145.62,0,0,1,92.4,107.81a51.33,51.33,0,0,0,15.88,68.47A50.91,50.91,0,0,1,85,169.86c0,.21,0,.43,0,.65a51.31,51.31,0,0,0,41.15,50.28,51.21,51.21,0,0,1-23.16.88,51.35,51.35,0,0,0,47.92,35.62,102.92,102.92,0,0,1-63.7,22A104.41,104.41,0,0,1,75,278.55a145.21,145.21,0,0,0,78.62,23" fill="#fff"/>
      </svg>
    </a>
</div>

<div class="content" role="main">

  <!-- Highlight Card -->
  <div class="card highlight-card card-small">

    <svg id="rocket" alt="Rocket Ship" xmlns="http://www.w3.org/2000/svg" width="101.678" height="101.678" viewBox="0 0 101.678 101.678">
      <g id="Group_83" data-name="Group 83" transform="translate(-141 -696)">
        <circle id="Ellipse_8" data-name="Ellipse 8" cx="50.839" cy="50.839" r="50.839" transform="translate(141 696)" fill="#dd0031"/>
        <g id="Group_47" data-name="Group 47" transform="translate(165.185 720.185)">
          <path id="Path_33" data-name="Path 33" d="M3.4,42.615a3.084,3.084,0,0,0,3.553,3.553,21.419,21.419,0,0,0,12.215-6.107L9.511,30.4A21.419,21.419,0,0,0,3.4,42.615Z" transform="translate(0.371 3.363)" fill="#fff"/>
          <path id="Path_34" data-name="Path 34" d="M53.3,3.221A3.09,3.09,0,0,0,50.081,0,48.227,48.227,0,0,0,18.322,13.437c-6-1.666-14.991-1.221-18.322,7.218A33.892,33.892,0,0,1,9.439,25.1l-.333.666a3.013,3.013,0,0,0,.555,3.553L23.985,43.641a2.9,2.9,0,0,0,3.553.555l.666-.333A33.892,33.892,0,0,1,32.647,53.3c8.55-3.664,8.884-12.326,7.218-18.322A48.227,48.227,0,0,0,53.3,3.221ZM34.424,9.772a6.439,6.439,0,1,1,9.106,9.106,6.368,6.368,0,0,1-9.106,0A6.467,6.467,0,0,1,34.424,9.772Z" transform="translate(0 0.005)" fill="#fff"/>
        </g>
      </g>
    </svg>

    <span>{{ title }} app is running!</span>

    <svg id="rocket-smoke" alt="Rocket Ship Smoke" xmlns="http://www.w3.org/2000/svg" width="516.119" height="1083.632" viewBox="0 0 516.119 1083.632">
      <path id="Path_40" data-name="Path 40" d="M644.6,141S143.02,215.537,147.049,870.207s342.774,201.755,342.774,201.755S404.659,847.213,388.815,762.2c-27.116-145.51-11.551-384.124,271.9-609.1C671.15,139.365,644.6,141,644.6,141Z" transform="translate(-147.025 -140.939)" fill="#f5f5f5"/>
    </svg>

  </div>

  <!-- Resources -->
  <h2>Resources</h2>
  <p>Here are some links to help you get started:</p>

  <div class="card-container">
    <a class="card" target="_blank" rel="noopener" href="https://angular.io/tutorial">
      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M5 13.18v4L12 21l7-3.82v-4L12 17l-7-3.82zM12 3L1 9l11 6 9-4.91V17h2V9L12 3z"/></svg>

      <span>Learn Angular</span>

      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M10 6L8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg>    </a>

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      <span>CLI Documentation</span>

      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M10 6L8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg>
    </a>

    <a class="card" target="_blank" rel="noopener" href="https://blog.angular.io/">
      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M13.5.67s.74 2.65.74 4.8c0 2.06-1.35 3.73-3.41 3.73-2.07 0-3.63-1.67-3.63-3.73l.03-.36C5.21 7.51 4 10.62 4 14c0 4.42 3.58 8 8 8s8-3.58 8-8C20 8.61 17.41 3.8 13.5.67zM11.71 19c-1.78 0-3.22-1.4-3.22-3.14 0-1.62 1.05-2.76 2.81-3.12 1.77-.36 3.6-1.21 4.62-2.58.39 1.29.59 2.65.59 4.04 0 2.65-2.15 4.8-4.8 4.8z"/></svg>

      <span>Angular Blog</span>

      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M10 6L8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg>
    </a>

  </div>

  <!-- Next Steps -->
  <h2>Next Steps</h2>
  <p>What do you want to do next with your app?</p>

  <input type="hidden" #selection>

  <div class="card-container">
    <div class="card card-small" (click)="selection.value = 'component'" tabindex="0">
        <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>

      <span>New Component</span>
    </div>

    <div class="card card-small" (click)="selection.value = 'material'" tabindex="0">
        <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>

      <span>Angular Material</span>
    </div>

    <div class="card card-small" (click)="selection.value = 'pwa'" tabindex="0">
        <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>

      <span>Add PWA Support</span>
    </div>

    <div class="card card-small" (click)="selection.value = 'dependency'" tabindex="0">
      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>

      <span>Add Dependency</span>
    </div>

    <div class="card card-small" (click)="selection.value = 'test'" tabindex="0">
      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>

      <span>Run and Watch Tests</span>
    </div>

    <div class="card card-small" (click)="selection.value = 'build'" tabindex="0">
      <svg class="material-icons" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"><path d="M19 13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/></svg>

      <span>Build for Production</span>
    </div>
  </div>

  <!-- Terminal -->
  <div class="terminal" [ngSwitch]="selection.value">
      <pre *ngSwitchDefault>ng generate component xyz</pre>
      <pre *ngSwitchCase="'material'">ng add @angular/material</pre>
      <pre *ngSwitchCase="'pwa'">ng add @angular/pwa</pre>
      <pre *ngSwitchCase="'dependency'">ng add _____</pre>
      <pre *ngSwitchCase="'test'">ng test</pre>
      <pre *ngSwitchCase="'build'">ng build --prod</pre>
  </div>

  <!-- Links -->
  <div class="card-container">
    <a class="circle-link" title="Animations" href="https://angular.io/guide/animations" target="_blank" rel="noopener">
      <svg id="Group_20" data-name="Group 20" xmlns="http://www.w3.org/2000/svg" width="21.813" height="23.453" viewBox="0 0 21.813 23.453">
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        <path id="Path_16" data-name="Path 16" d="M4181.516,972.736v23.453l9.245-5.153,1.686-14.4Z" transform="translate(-4170.633 -972.736)" fill="#fb8c00"/>
        <path id="Path_17" data-name="Path 17" d="M4137.529,1076.127l-7.7-3.723,4.417-2.721,7.753,3.723Z" transform="translate(-4125.003 -1058.315)" fill="#ffe0b2"/>
        <path id="Path_18" data-name="Path 18" d="M4137.529,1051.705l-7.7-3.723,4.417-2.721,7.753,3.723Z" transform="translate(-4125.003 -1036.757)" fill="#fff3e0"/>
        <path id="Path_19" data-name="Path 19" d="M4137.529,1027.283l-7.7-3.723,4.417-2.721,7.753,3.723Z" transform="translate(-4125.003 -1015.199)" fill="#fff"/>
      </svg>
    </a>

    <a class="circle-link" title="CLI" href="https://cli.angular.io/" target="_blank" rel="noopener">
      <svg alt="Angular CLI Logo" xmlns="http://www.w3.org/2000/svg" width="21.762" height="23.447" viewBox="0 0 21.762 23.447">
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          <path id="Path_20" data-name="Path 20" d="M2660.313,313.618h0l-10.833,3.9,1.637,14.4,9.2,5.152,9.244-5.152,1.685-14.4Z" transform="translate(-2649.48 -313.618)" fill="#37474f"/>
          <path id="Path_21" data-name="Path 21" d="M2741.883,313.618v23.447l9.244-5.152,1.685-14.4Z" transform="translate(-2731.05 -313.618)" fill="#263238"/>
          <path id="Path_22" data-name="Path 22" d="M2692.293,379.169h11.724V368.618h-11.724Zm11.159-.6h-10.608v-9.345h10.621v9.345Z" transform="translate(-2687.274 -362.17)" fill="#fff"/>
          <path id="Path_23" data-name="Path 23" d="M2709.331,393.688l.4.416,2.265-2.28-2.294-2.294-.4.4,1.893,1.893Z" transform="translate(-2702.289 -380.631)" fill="#fff"/>
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    <a class="circle-link" title="Augury" href="https://augury.rangle.io/" target="_blank" rel="noopener">
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        <defs>
          <clipPath id="clip-path">
            <rect id="Rectangle_13" data-name="Rectangle 13" width="10.338" height="10.27" fill="none"/>
          </clipPath>
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Como vimos en el concepto anterior cambiamos el contenido de este archivo por:

<h1 style="text-align:center">
  Bienvenido a {{ title }}
</h1>

Analizaremos ahora de este trozo de HTML donde aparece el atributo 'title' de la componente:

  Bienvenido a {{ title }}

Cuando ejecutamos nuestra aplicación desde la línea de comandos de Node.js:

ejecución de proyecto en Angular

En el navegador aparece el contenido de la propiedad 'title':

propiedad title

Podemos ver que aparece el string 'proyecto001' y no {{ title }}:

  title = 'proyecto001';

Este concepto de sustitución se llama interpolación y lo veremos en forma más profunda en el concepto siguiente.

Otro archivo que se asocia a la componente 'AppComponent' es 'app.component.css' donde se almacenan todos los estilos que se van a aplicar solo a dicha componente, es decir que quedarán encapsulados en la componente 'AppComponent'.

En la carpeta raíz del proyecto hay un archivo llamado 'styles.css' donde podemos definir estilos que se aplicarán en forma global a todas las componentes de nuestra aplicación:

angular styles.css

Ya hemos nombrado los tres archivos fundamentales que definen toda componente:

app.component.ts
app.component.html
app.component.css

Queda uno llamado 'app.component.spec.ts' que tiene por objetivo definir código de testing para medir el correcto funcionamiento de la componente (dejaremos para más adelante este concepto)

Otro archivo fundamental que nos crea Angular CLI es 'app.module.ts' en la misma carpeta donde se encuentran los 4 archivos de la componente 'AppComponent':

app.module.ts

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';


import { AppComponent } from './app.component';


@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Nombramos este archivo porque como mínimo una aplicación en Angular debe tener un módulo. Podemos ver que en la función @NgModule en la propiedad 'declarations' se le pasa un vector con un elemento que es nuestra componente 'AppComponent'.

La aplicación mínima en Angular debe tener un módulo y dentro de dicho módulo como mínimo una componente:

módulo y componente

Un proyecto grande se divide en diferentes módulos con un conjunto de componentes cada uno.

Por ejemplo podemos tener un módulo 'Clientes' con tres componentes que resuelven distintas partes visuales de la aplicación:

módulo y componente

En los primeros conceptos de este tutorial estaremos trabajando con la única componente 'AppComponent' y más adelante veremos como crear más componentes en el módulo 'AppModule' e inclusive como crear más módulos.

Hay muchos más archivos y carpetas en el proyecto que nos crea Angular CLI pero iremos viendo su objetivo a medida que avancemos en el curso.