Las insignias se usan para transmitir información que no es urgente al usuario. Por ejemplo, se usan para indicar el estado de una app o la cantidad de elementos no leídos. La forma clásica de crear una insignia de app es agregar un número al ícono de página. En los navegadores actualizados, después de instalar una app, hay una forma integrada de agregar una insignia al ícono de la app en la barra de tareas del sistema operativo.
A la manera moderna
Usa el método navigator.setAppBadge()
El método navigator.setAppBadge() establece una insignia en el ícono asociado con la app instalada. El método toma un solo argumento opcional, que es un número entero que se usará como valor de la insignia. Si lo estableces en 0,
se borrará la insignia de la app. Si no proporcionas un argumento, se generará una insignia genérica que, por lo general, se muestra como un punto de color.
El método clásico
Cómo agregar un número al ícono de página
Si la app aún no está instalada, puedes agregar un número al ícono de página. Existen muchas formas de hacerlo, por ejemplo, puedes dibujar el ícono de página de forma dinámica en un lienzo con la información de la insignia agregada y mostrarla como una URL de BLOB, o crear una imagen SVG con la información de la insignia como una URL de datos.
Mejora progresiva
El siguiente fragmento usa un elemento personalizado <favicon-badge></favicon-badge> que le permite al desarrollador establecer de forma declarativa una insignia en el ícono de página especificado mediante el atributo src pasando un número entero al atributo badge. Cuando el usuario instala la app, la insignia se "actualiza" a una insignia de sistema operativo nativo.
import 'https://unpkg.com/favicon-badge@2.0.0/dist/FavIconBadge.js';
// DOM references.
const favicon = document.querySelector('favicon-badge');
const installButton = document.querySelector('button');
// Feature detection.
const supportsAppBadge = 'setAppBadge' in navigator;
let setAppBadge;
// For the demo simply set the badge between [0, 9].
let i = 0;
const getAppBadgeValue = () => {
if (i > 9) {
i = 0;
}
return i++;
};
// Set the badge on the favicon.
const setAppBadgeFavicon = (value) => {
favicon.badge = value;
};
// Set the native operating system badge.
const setAppBadgeNative = (value) => {
navigator.setAppBadge(value);
}
// If the app is installed and the Badging API is supported,
// set the badge on the native operating system. Else, fall
// back to the favicon.
if (
matchMedia('(display-mode: standalone)').matches &&
supportsAppBadge
) {
setAppBadge = setAppBadgeNative;
} else {
setAppBadge = setAppBadgeFavicon;
}
// Set a new badge every second.
setInterval(() => {
setAppBadge(getAppBadgeValue());
}, 1000);
// If installation is supported…
if ('BeforeInstallPromptEvent' in window) {
let installEvent = null;
const onInstall = () => {
// After installation, "upgrade" to the native operating system badge.
installButton.disabled = true;
installEvent = null;
if (supportsAppBadge) {
favicon.badge = false;
setAppBadge = setAppBadgeNative;
}
};
// …listen for the `beforeinstallprompt` event.
window.addEventListener('beforeinstallprompt', (event) => {
event.preventDefault();
installEvent = event;
installButton.disabled = false;
});
// Deal with installation.
installButton.addEventListener('click', async () => {
if (!installEvent) {
return;
}
installEvent.prompt();
const result = await installEvent.userChoice;
if (result.outcome === 'accepted') {
onInstall();
}
});
// Listen for the `appinstalled` in case the user installs the app manually.
window.addEventListener('appinstalled', (event) => {
onInstall();
});
}
Lecturas adicionales
Demostración
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="manifest" href="manifest.json" />
<title>How to create an app badge</title>
<link rel="stylesheet" href="style.css" />
<!-- TODO: Devsite - Removed inline handlers -->
<!-- <script>
if ('serviceWorker' in navigator) {
window.addEventListener('load', async () => {
const registration = await navigator.serviceWorker.register(
'sw.js',
);
console.log(
'Service worker registered for scope',
registration.scope,
);
});
}
</script>
<script src="script.js" type="module"></script> -->
</head>
<body>
<h1>How to create an app badge</h1>
<ol>
<li>
Watch the favicon. You should see a counter that updates each second
integrated into the favicon.
<img
src="../favicon.png"
style="width: 250px; height: auto"
width="528"
height="74"
alt="Favicon with counter."
/>
</li>
<li>
Install the app by clicking the button below. After the installation,
the button is disabled.
<p>
<button disabled type="button">Install</button>
</p>
</li>
<li>
Watch the app icon in your operating system's task bar. You should see a
counter that updates each second as an app badge.
<img
src="../app-badge.png"
style="width: 80px; height: auto"
width="282"
height="388"
alt="App badge with counter."
/>
</li>
</ol>
<favicon-badge src="../favicon.svg" textColor="#fff" badge="" />
</body>
</html>CSS
html {
box-sizing: border-box;
font-family: system-ui, sans-serif;
color-scheme: dark light;
}
*, *:before, *:after {
box-sizing: inherit;
}
body {
margin: 1rem;
}
img {
height: auto;
max-width: 100%;
display: block;
}
JS
import 'https://unpkg.com/favicon-badge@2.0.0/dist/FavIconBadge.js';
// The `` custom element.
const favicon = document.querySelector('favicon-badge');
// The install button.
const installButton = document.querySelector('button');
// Feature detection.
const supportsAppBadge = 'setAppBadge' in navigator;
// This function will either set the favicon or the native
// app badge. The implementation is dynamically changed at runtime.
let setAppBadge;
// Variable for the counter.
let i = 0;
// Returns a value between 0 and 9.
const getAppBadgeValue = () => {
if (i > 9) {
i = 0;
}
return i++;
};
// Function to set a favicon badge.
const setAppBadgeFavicon = (value) => {
favicon.badge = value;
};
// Function to set a native app badge.
const setAppBadgeNative = (value) => {
navigator.setAppBadge(value);
}
// If the app is installed and native app badges are supported,
// use the native app badge.
if (
matchMedia('(display-mode: standalone)').matches &&
supportsAppBadge
) {
setAppBadge = setAppBadgeNative;
// In all other cases (i.e., if the app is not installed or native
// app badges are not supported), use the favicon badge.
} else {
setAppBadge = setAppBadgeFavicon;
}
// Update the badge every second.
setInterval(() => {
setAppBadge(getAppBadgeValue());
}, 1000);
// Only relevant for browsers that support installation.
if ('BeforeInstallPromptEvent' in window) {
// Variable to stash the `BeforeInstallPromptEvent`.
let installEvent = null;
// Function that will be run when the app is installed.
const onInstall = () => {
// Disable the install button.
installButton.disabled = true;
// No longer needed.
installEvent = null;
if (supportsAppBadge) {
// Remove the favicon badge.
favicon.badge = false;
// Switch the implementation so it uses the native
// app badge.
setAppBadge = setAppBadgeNative;
}
};
window.addEventListener('beforeinstallprompt', (event) => {
// Do not show the install prompt quite yet.
event.preventDefault();
// Stash the `BeforeInstallPromptEvent` for later.
installEvent = event;
// Enable the install button.
installButton.disabled = false;
});
installButton.addEventListener('click', async () => {
// If there is no stashed `BeforeInstallPromptEvent`, return.
if (!installEvent) {
return;
}
// Use the stashed `BeforeInstallPromptEvent` to prompt the user.
installEvent.prompt();
const result = await installEvent.userChoice;
// If the user installs the app, run `onInstall()`.
if (result.outcome === 'accepted') {
onInstall();
}
});
// The user can decide to ignore the install button
// and just use the browser prompt directly. In this case
// likewise run `onInstall()`.
window.addEventListener('appinstalled', (event) => {
onInstall();
});
}