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Creación de elementos del DOM1/8
A la lista de tareas
  1. 1. Comentarios para un portal de noticias
  2. 2. El método append y la inserción de contenido
  3. 3. El método createElement y la creación de elementos
  4. 4. Añadimos un elemento a la página
  5. 5. Añadimos un comentario al enviar el formulario
  6. 6. Cambiamos las propiedades del elemento que creamos
  7. 7. Tomamos el texto del comentario del campo de entrada
  8. 8. Limpiamos el campo de entrada después de enviar
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Comentarios para un portal de noticias

Las noticias no solo se leen: también se comentan. Por eso Muffin decidió añadir comentarios anónimos al sitio. Los desarrolladores ya habían empezado el trabajo, pero no llegaron a terminarlo. Ahora nos toca terminarlo.

En la página de la noticia ya hay un hilo de comentarios y un formulario para añadir uno nuevo. Los programadores ya encontraron el formulario con JavaScript, lo guardaron en la variable commentForm y le asignaron un manejador de eventos. El script que necesitamos está en comments.js.

Los comentarios deben aparecer dentro del elemento con la clase comment-list. Ahora mismo ya hay uno:

<ol class="comment-list">
  <li class="user-comment">Venga ya, qué tontería...</li>
</ol>

Para empezar, vamos a encontrar ese elemento, guardarlo en una variable y cambiar su contenido de texto. Así veremos al instante cómo JavaScript modifica el texto en la página.

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    <!DOCTYPE html> <html lang="es"> <head> <meta charset="utf-8"> <link rel="stylesheet" href="setting.css"> <link rel="stylesheet" href="style.css"> <title>FlashNews!</title> </head> <body class="page light-theme"> <header class="page-header"> <div class="container"> <span class="header-logo"> <img src="img/main-logo.svg" width="67" height="29" alt="Logotipo del portal FlashNews!"> </span> <button class="theme-button" type="button">Cambiar tema</button> </div> </header> <main class="inner-news"> <article class="container"> <h1 class="inner-heading">🔥 ¡Impacto! ¡Escándalo! ¡Sensación!</h1> <div class="news-full"> <img src="img/news-robot2.jpg" alt="Robot de vacaciones"> <div class="news-stats"> <button class="heart" type="button"><span class="likes-number">9</span></button> <time datetime="2019-12-22">22 dic 2019</time> </div> <p>Resulta que, para empezar a programar en JavaScript, no hace falta ser un gato. Un grupo de científicos creó el primer robot capaz de desarrollarse y cambiar su propio código. Enseguida aprendió a maquetar sitios web y se fue a trabajar como freelance a Bali.</p> </div> </article> <section class="comment-feed container"> <h2>Comentarios</h2> <ol class="comment-list"> <li class="user-comment">No puede ser, qué tontería...</li> </ol> <form action="https://echo.codigoheroe.com/courses" method="post" class="comment-form"> <div class="comment-inner"> <label class="comment-label" for="comment-input">Tu comentario</label> <input type="text" class="comment-field" placeholder="Comentario" required id="comment-input"> </div> <button class="button" type="submit">Enviar</button> </form> </section> </main> <footer class="page-footer"> <div class="container"> <p>© FlashNews!</p> <span class="footer-logo"> <img src="img/white-logo.svg" alt="Logotipo del portal FlashNews!"> </span> </div> </footer> <script src="themes.js"></script> <script src="likes.js"></script> <script src="comments.js"></script> </body> </html>
    /* estilos de la página de noticias */ .comment-form { display: flex; margin-bottom: 30px; padding: 20px 12px; } .comment-inner { position: relative; flex-grow: 1; margin-right: 10px; } .comment-label { position: absolute; top: -16px; left: -9px; padding: 4px 8px; font-size: 10px; line-height: 14px; } .comment-field { width: 100%; height: 30px; padding: 0 10px; border: none; background-color: transparent; font: inherit; font-size: 14px; line-height: 30px; } .comment-field::placeholder { color: #aaaaaa; font: inherit; font-size: 14px; font-style: italic; } .comment-field:focus::placeholder { font-size: 0; } .comment-field:hover::placeholder, .comment-field:active::placeholder { opacity: 0.5; } .inner-news .inner-heading { margin-bottom: 20px; font-size: 24px; } .news-full { display: flex; flex-direction: column; margin-bottom: 24px; } .news-full img { margin-bottom: 4px; width: 100%; height: 220px; object-fit: cover; } .news-full .news-stats { display: flex; justify-content: space-between; } .news-full .heart { padding: 12px 10px; min-width: 40px; min-height: 34px; font-family: inherit; font-weight: bold; font-size: 16px; border: none; background-color: transparent; background-repeat: no-repeat; background-position: 12px; cursor: pointer; } .heart .likes-number { margin-left: 24px; line-height: 14px; } .news-full time { margin-top: 14px; margin-right: 12px; margin-bottom: 8px; margin-left: 0; } .news-full p { margin-top: 0; margin-right: 12px; margin-bottom: 16px; margin-left: 12px; font-size: 14px; line-height: 24px; } .comment-feed h2 { margin-top: 0; margin-bottom: 12px; } .comment-list { margin-top: 0; margin-right: 0; margin-bottom: 12px; margin-left: 0; padding: 0; list-style: none; counter-reset: comments; } .comment-list li { margin-bottom: 6px; padding: 10px 12px; min-height: 36px; font-size: 14px; line-height: 24px; } .comment-list .user-comment { position: relative; display: flex; } .comment-list .user-comment::before { counter-increment: comments; content: "#" counter(comments); padding-right: 12px; margin-right: 12px; border-right: 1px solid; font-weight: bold; } .comment-list .user-comment::after { position: absolute; content: ""; width: 0; height: 0; bottom: 0; left: -8px; border: 4px solid; border-left-color: transparent; border-top-color: transparent; } @keyframes comment-blink-light { 0% { background-color: #b6aaff; opacity: 0; } 20% { opacity: 0.8; } } @keyframes comment-blink-light-after { 0% { border-right-color: #b6aaff; border-bottom-color: #b6aaff; opacity: 0; } 20% { opacity: 0.8; } } @keyframes comment-blink-dark { 0% { background-color: #473c8d; opacity: 0; } 20% { opacity: 1; } } @keyframes comment-blink-dark-after { 0% { border-right-color: #473c8d; border-bottom-color: #473c8d; opacity: 0; } 20% { opacity: 1; } } /* temas */ .dark-theme .header-logo { filter: invert(1) hue-rotate(180deg) brightness(2); } /* Tema claro */ .light-theme { color: #333333; background-color: #eae9f2; } .light-theme .page-header { background-color: #ffffff; box-shadow: 0 2px 2px rgba(0, 0, 0, 0.2); } .light-theme .header-link { color: #6653d9; } .light-theme .header-link::before { background-image: url("img/arrow-back-light.svg"); background-repeat: no-repeat; background-position: 0 0; } .light-theme .theme-button { color: #6653d9; border: 1px solid #6653d9; } .light-theme .theme-button::before { background-image: url("img/moon-normal.svg"); } .light-theme .theme-button:focus, .light-theme .theme-button:hover { color: #ffffff; background-color: #6653d9; } .light-theme .theme-button:focus { outline-color: #b6aaff; } .light-theme .theme-button:focus::before, .light-theme .theme-button:hover::before { background-image: url("img/moon-hover.svg"); } .light-theme .menu-open { background-color: #ffffff; background-image: url("img/menu-open-light.svg"); } .light-theme .menu:focus { outline-color: #b6aaff; } .light-theme .menu-open:focus, .light-theme .menu-open:hover { background-color: #6653d9; background-image: url("img/menu-open-dark.svg"); } .light-theme .menu-close { background-color: #6653d9; } .light-theme .menu-close:focus, .light-theme .menu-close:hover { background-color: #473c8d; } .light-theme .main-menu { background-color: #6653d9; color: #ffffff; } .light-theme .main-menu a:focus, .light-theme .main-menu a:hover { background-color: #473c8d; } .light-theme .main-menu a:focus { outline-color: #b6aaff; } .light-theme .news-view button { border: 1px solid #6653d9; color: #6653d9; } .light-theme .news-view button:focus, .light-theme .news-view button:hover, .light-theme .news-view button:active, .light-theme .news-view .view-checked { background-color: #6653d9; color: #ffffff; } .light-theme .news-view button:focus { outline-color: #b6aaff; } .light-theme .news-view .row-view:focus::before, .light-theme .news-view .row-view:hover::before, .light-theme .news-view .row-view:active::before { background-image: url("img/rows-light-checked.svg"); } .light-theme .news-view .tile-view:focus::before, .light-theme .news-view .tile-view:hover::before, .light-theme .news-view .tile-view:active::before { background-image: url("img/tiles-light-checked.svg"); } .light-theme .row-view::before { background-image: url("img/rows-light.svg"); } .light-theme .tile-view::before { background-image: url("img/tiles-light.svg"); } .light-theme .row-view.view-checked::before { background-image: url("img/rows-light-checked.svg"); } .light-theme .tile-view.view-checked::before { background-image: url("img/tiles-light-checked.svg"); } .light-theme .new-block { background-color: #ffffff; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2); } .light-theme .news-full { background-color: #ffffff; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2); } .light-theme .new-block time { color: #aaaaaa; } .light-theme .news-full time { color: #aaaaaa; } .light-theme .cookies-agreement { background-color: #fdeacd; box-shadow: 0 -1px 4px rgba(0, 0, 0, 0.2); } .light-theme .button { background-color: #6653d9; color: #ffffff; } .light-theme .button:focus, .light-theme .button:hover { background-color: #473c8d; } .light-theme .button:focus { outline-color: #b6aaff; } .light-theme .page-footer { background-color: #6653d9; color: #ffffff; } .light-theme .subscription, .light-theme .comment-form { background-color: #ffffff; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2); } .light-theme .subscription-message { background-color: #6653d9; color: #eae9f2; } .light-theme .subscription-message::before { background-image: url("img/icon-ok-light.svg"); } .light-theme .subscription-label, .light-theme .comment-label { color: #6653d9; } .light-theme .subscription-email, .light-theme .comment-field { border: 1px solid #eae9f2; color: #333333; } .light-theme .heart { color: #6653d9; background-image: url("img/icon-heart-light.svg"); opacity: 0.7; } .light-theme .heart.added { background-image: url("img/icon-heart-light-added.svg"); } .page .heart:focus, .page .heart:hover { opacity: 1; } .light-theme .heart:focus { outline-color: #b6aaff; } .light-theme .heart:active { opacity: 1; background-image: url("img/icon-heart-light-active.svg"); } .light-theme .comment-list li { background-color: #ffffff; } .light-theme .user-comment:not(:first-child) { animation: comment-blink-light 600ms ease-in; } .light-theme .user-comment::before { border-right-color: #eae9f2; color: #cdcdcd; } .light-theme .user-comment::after { border-right-color: #ffffff; border-bottom-color: #ffffff; } .light-theme .user-comment:not(:first-child)::after { animation: comment-blink-light-after 600ms ease-in; } .light-theme .comment-label { background-color: #ffffff; } .light-theme .comment-field:focus { outline-color: #b6aaff; } /* Tema oscuro */ .dark-theme { color: #f2f2f2; background-color: #17161a; } .dark-theme .page-header { background-color: #373540; box-shadow: 0 2px 2px rgba(0, 0, 0, 0.6); } .dark-theme .header-link { color: #9484f2; } .dark-theme .header-link::before { background-image: url("img/arrow-back-dark.svg"); background-repeat: no-repeat; background-position: 0 0; } .dark-theme .theme-button { color: #9484f2; border: 1px solid #9484f2; } .dark-theme .theme-button::before { background-image: url("img/sun-normal.svg"); } .dark-theme .theme-button:focus, .dark-theme .theme-button:hover { color: #17161a; background-color: #9484f2; } .dark-theme .theme-button:focus { outline-color: #6653d9; } .dark-theme .theme-button:focus::before, .dark-theme .theme-button:hover::before { background-image: url("img/sun-hover.svg"); } .dark-theme .menu:focus { outline-color: #6653d9; } .dark-theme .menu-open { background-color: #373540; background-image: url("img/menu-open-dark.svg"); } .dark-theme .menu-open:focus, .dark-theme .menu-open:hover { background-color: #473c8d; background-image: url("img/menu-open-dark.svg"); } .dark-theme .menu-close { background-color: #473c8d; } .dark-theme .menu-close:focus, .dark-theme .menu-close:hover { background-color: #6653d9; } .dark-theme .main-menu { background-color: #473c8d; color: #f2f2f2; } .dark-theme .main-menu a:focus { outline-color: #6653d9; } .dark-theme .main-menu a:focus, .dark-theme .main-menu a:hover { background-color: #6653d9; } .dark-theme .news-view button { border: 1px solid #9484f2; color: #9484f2; } .dark-theme .news-view button:focus { outline-color: #6653d9; } .dark-theme .news-view button:focus, .dark-theme .news-view button:hover, .dark-theme .news-view button:active, .dark-theme .news-view .view-checked { background-color: #9484f2; color: #17161a; } .dark-theme .news-view .row-view:focus::before, .dark-theme .news-view .row-view:hover::before, .dark-theme .news-view .row-view:active::before { background-image: url("img/rows-dark-checked.svg"); } .dark-theme .news-view .tile-view:focus::before, .dark-theme .news-view .tile-view:hover::before, .dark-theme .news-view .tile-view:active::before { background-image: url("img/tiles-dark-checked.svg"); } .dark-theme .row-view::before { background-image: url("img/rows-dark.svg"); } .dark-theme .tile-view::before { background-image: url("img/tiles-dark.svg"); } .dark-theme .row-view.view-checked::before { background-image: url("img/rows-dark-checked.svg"); } .dark-theme .tile-view.view-checked::before { background-image: url("img/tiles-dark-checked.svg"); } .dark-theme .new-block { background-color: #2a2930; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.6); } .dark-theme .news-full { background-color: #2a2930; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.6); } .dark-theme .new-block time { color: #888888; } .dark-theme .news-full time { color: #888888; } .dark-theme .cookies-agreement { background-color: #473c8d; box-shadow: 0 -1px 4px rgba(0, 0, 0, 0.6); } .dark-theme .button { background-color: #9484f2; color: #17161a; } .dark-theme .button:focus { outline-color: #6653d9; } .dark-theme .button:focus, .dark-theme .button:hover { background-color: #b6aaff; } .dark-theme .page-footer { background-color: #0a0910; color: #f2f2f2; } .dark-theme .subscription, .dark-theme .comment-form { background-color: #2a2930; box-shadow: 0 1px 4px rgba(0, 0, 0, 0.6); } .dark-theme .subscription-message { background-color: #9484f2; color: #17161a; } .dark-theme .subscription-message::before { background-image: url("img/icon-ok-dark.svg"); } .dark-theme .subscription-label, .dark-theme .comment-label { color: #9484f2; } .dark-theme .comment-label { background-color: #2a2930; } .dark-theme .subscription-email, .dark-theme .comment-field { border: 1px solid #473c8d; color: #f2f2f2; } .dark-theme .heart { color: #9484f2; background-image: url("img/icon-heart-dark.svg"); opacity: 0.7; } .dark-theme .heart:focus { outline-color: #6653d9; } .dark-theme .heart.added { background-image: url("img/icon-heart-dark-added.svg"); } .dark-theme .heart:active { opacity: 1; background-image: url("img/icon-heart-dark-active.svg"); } .dark-theme .comment-list li { background-color: #2a2930; } .dark-theme .user-comment:not(:first-child) { animation: comment-blink-dark 600ms ease-in; } .dark-theme .user-comment::before { border-right-color: #17161a; color: rgba(255, 255, 255, 0.3); } .dark-theme .user-comment::after { border-right-color: #2a2930; border-bottom-color: #2a2930; } .dark-theme .user-comment:not(:first-child)::after { animation: comment-blink-dark-after 600ms ease-in; } .dark-theme .comment-field:focus { outline-color: #6653d9; }
    let commentForm = document.querySelector('.comment-form'); // Declara la variable aquí commentForm.onsubmit = function (evt) { evt.preventDefault(); };
    let page = document.querySelector('.page'); let themeButton = document.querySelector('.theme-button'); themeButton.onclick = function () { page.classList.toggle('light-theme'); page.classList.toggle('dark-theme'); };
    let heart = document.querySelector('.heart'); let likesNumber = document.querySelector('.likes-number'); heart.onclick = function () { if (heart.classList.contains('added')) { likesNumber.textContent--; } else { likesNumber.textContent++; } heart.classList.toggle('added'); };

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    ObjetivosRealizado
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      1. En la línea 2, declara la variable commentList y guarda en ella el elemento con la clase comment-list.
      2. En la línea siguiente, asigna a commentList.textContent el valor 'Nuevo comentario'. Fíjate en que el comentario anterior ha desaparecido del hilo.

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