Tarea anterior
Creación de elementos del DOM2/8
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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El método append y la inserción de contenido

En la tarea anterior cambiamos textContent del elemento commentList y, por eso, borramos el comentario anterior. Así funciona textContent: sustituye todo el contenido del elemento. Para una lista de comentarios no nos sirve, porque los mensajes nuevos deben aparecer después de los viejos. Aquí nos ayuda el método append:

elementoPadre.append(elementoQueSeAñade);

El método append añade contenido nuevo al final del elemento y no elimina nada de lo que ya había. Con él puedes añadir tanto elementos como cadenas de texto.

Por ejemplo, imagina que en la página hay este párrafo:

<p>Qué bien es vivir como un gato.</p>

Lo buscamos y llamamos a append:

let paragraph = document.querySelector('p');
paragraph.append(' ¡Pero ser desarrollador es aún mejor!');

Después, el marcado quedará así:

<p>Qué bien es vivir como un gato. ¡Pero ser desarrollador es aún mejor!</p>

La nueva cadena se ha añadido al final y el texto anterior se ha quedado en su sitio. Justo lo que necesitamos para los comentarios. Ahora toca añadir una cadena al final del hilo.

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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">26</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'); let commentList = document.querySelector('.comment-list'); commentList.textContent = 'Nuevo comentario'; 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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      1. Sustituye el código de la línea 3 por commentList.append('Nuevo comentario');.
        Fíjate en que el texto nuevo ha aparecido después del comentario anterior.

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