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- Teoría
- Teoría
Usar la estructura condicional if
Ya aprendieron a comprobar si un elemento tiene una clase. Ahora hay que hacer que JavaScript disminuya el número del contador cuando la clase esté presente y lo aumente cuando no lo esté. Para eso vamos a usar una estructura condicional.
Una estructura condicional permite ejecutar acciones según una condición y se escribe así:
if (condición) {
// Instrucciones que se ejecutarán si la condición es verdadera
}La condición se escribe entre paréntesis después de la palabra if. Una condición es una instrucción que devuelve true o false. Dentro de las llaves se escriben las instrucciones que deben ejecutarse cuando la condición devuelve true.
Por ejemplo:
let element = document.querySelector('div');
if (element.classList.contains('some-class')) {
// El mensaje se mostrará solo si el elemento tiene la clase
console.log('La condición es verdadera');
}Si el elemento heart tiene la clase added, significa que la persona usuaria ya dejó su Me gusta y ahora quiere quitarlo. En ese caso, debemos disminuir el valor del contador. Añadan al script una estructura condicional: si el elemento tiene la clase, el contador debe disminuir en 1.
Todos los archivos
<!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"></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>
</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>
</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 heart = document.querySelector('.heart');
let likesNumber = document.querySelector('.likes-number');
let counter = 0;
heart.onclick = function () {
console.log(heart.classList.contains('added'));
counter++;
likesNumber.textContent = counter;
heart.classList.toggle('added');
};
let page = document.querySelector('.page');
let themeButton = document.querySelector('.theme-button');
themeButton.onclick = function () {
page.classList.toggle('light-theme');
page.classList.toggle('dark-theme');
};
El código ha cambiado, haz clic en "Actualizar" o activa la ejecución automática.
Ha ido a otra página
Haga clic dentro del mininavegador para poner el foco en esta ventana.
100%
Consola
- En la línea 6, sustituyan la salida a consola por la estructura condicional
if (heart.classList.contains('added')) { }. - Dentro de las llaves de esa estructura condicional, añadan este código:
counter--;. - Hagan clic dos veces en el «corazón».
Fíjense en que el contador ya no aumenta con cada clic.