Kā izveidot PWA no nulles ar HTML, CSS un JavaScript

Progresīvās tīmekļa lietotnes ir veids, kā šo vietējo lietotņu sajūtu ieviest tradicionālajā tīmekļa lietotnē. Izmantojot PWA, mēs varam uzlabot savu vietni ar mobilo lietotņu funkcijām, kas palielina lietojamību un piedāvā lielisku lietotāja pieredzi.

Šajā rakstā mēs izveidosim PWA no nulles ar HTML, CSS un JavaScript. Šīs tēmas mēs apskatīsim:

  • Kas ir progresīvā tīmekļa lietotne?
  • Atzīmes
  • Stils
  • Rādīt datus ar JavaScript
  • Tīmekļa lietotņu manifests
  • Kas ir apkalpojošais darbinieks?
  • Aktīvu kešatmiņa
  • Atnest aktīvus
  • Reģistrējiet apkalpojošo darbinieku
  • Pēdējās domas
  • Nākamie soļi

Tātad, sāksim ar svarīgu jautājumu: kāds heck ir PWA?

Kas ir progresīvā tīmekļa lietotne?

Progresīvā tīmekļa lietotne ir tīmekļa lietotne, kas lietotājiem nodrošina lietotnei līdzīgu pieredzi, izmantojot modernās tīmekļa iespējas. Galu galā tā ir tikai jūsu parastā vietne, kas darbojas pārlūkprogrammā ar dažiem uzlabojumiem. Tas dod jums iespēju:

  • Lai to instalētu mobilajā sākuma ekrānā
  • Lai piekļūtu tam bezsaistē
  • Lai piekļūtu kamerai
  • Lai saņemtu informatīvos paziņojumus
  • Lai veiktu fona sinhronizāciju

Un vēl daudz vairāk.

Tomēr, lai mūsu tradicionālo tīmekļa lietotni varētu pārveidot par PWA, mums tas ir nedaudz jāpielāgo, pievienojot tīmekļa lietojumprogrammas manifesta failu un pakalpojumu sniedzēju.

Neuztraucieties par šiem jaunajiem noteikumiem - mēs tos aplūkosim tālāk.

Pirmkārt, mums ir jāizveido mūsu tradicionālā tīmekļa lietotne. Tātad sāksim ar uzcenojumu.

Atzīmes

HTML fails ir salīdzinoši vienkāršs. Mēs visu iesaiņojam maintagā.

  • In index.html
       Dev'Coffee PWA     

Dev'Coffee

  • Home
  • About
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Un izveidojiet navigācijas joslu ar navtagu. Tad divar klasi .containerturēs mūsu kartes, kuras mēs vēlāk pievienosim ar JavaScript.

Tagad, kad mēs to esam aizmirsuši, veidosim to ar CSS.

Stils

Šeit, kā parasti, mēs sākam ar nepieciešamo fontu importēšanu. Tad mēs veiksim dažus atiestatījumus, lai novērstu noklusējuma darbību.

  • In css/style.css
@import url("//fonts.googleapis.com/css?family=Nunito:400,700&display=swap"); * { margin: 0; padding: 0; box-sizing: border-box; } body { background: #fdfdfd; font-family: "Nunito", sans-serif; font-size: 1rem; } main { max-width: 900px; margin: auto; padding: 0.5rem; text-align: center; } nav { display: flex; justify-content: space-between; align-items: center; } ul { list-style: none; display: flex; } li { margin-right: 1rem; } h1 { color: #e74c3c; margin-bottom: 0.5rem; } 

Pēc tam mēs ierobežojam mainelementa maksimālo platumu, 900pxlai tas izskatās labi uz liela ekrāna.

Navigācijas joslai es gribu, lai logotips būtu pa kreisi un saites pa labi. Tātad, lai navtagu padarītu par elastīgu konteineru, mēs justify-content: space-between;tos pielīdzinām.

  • In css/style.css
.container { display: grid; grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)); grid-gap: 1rem; justify-content: center; align-items: center; margin: auto; padding: 1rem 0; } .card { display: flex; align-items: center; flex-direction: column; width: 15rem auto; height: 15rem; background: #fff; box-shadow: 0 10px 20px rgba(0, 0, 0, 0.19), 0 6px 6px rgba(0, 0, 0, 0.23); border-radius: 10px; margin: auto; overflow: hidden; } .card--avatar { width: 100%; height: 10rem; object-fit: cover; } .card--title { color: #222; font-weight: 700; text-transform: capitalize; font-size: 1.1rem; margin-top: 0.5rem; } .card--link { text-decoration: none; background: #db4938; color: #fff; padding: 0.3rem 1rem; border-radius: 20px; } 

Mums būs vairākas kartes, tāpēc konteinera elementam tas tiks parādīts kā režģis. Un ar grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)), tagad mēs varam padarīt mūsu kartes, atsaucīgs, lai viņi izmanto vismaz 15remplatumu, ja ir pietiekami daudz vietas (un 1frja tā nav).

Lai tie izskatās jauki, mēs dubultojam ēnas efektu uz .cardklasi un izmantojam object-fit: cover, .card--avatarlai attēls netiktu izstiepts.

Tagad tas izskatās daudz labāk - bet mums joprojām nav datu, ko parādīt.

Labosim to nākamajā sadaļā

Rādīt datus ar JavaScript

Ievērojiet, ka es izmantoju lielus attēlus, kuru ielāde prasa zināmu laiku. Tas jums vislabākajā veidā parādīs apkalpojošo darbinieku spēku.

Kā jau teicu iepriekš, .containerklase turēs mūsu kārtis. Tāpēc mums tas ir jāizvēlas.

  • In js/app.js
const container = document.querySelector(".container") const coffees = [ { name: "Perspiciatis", image: "images/coffee1.jpg" }, { name: "Voluptatem", image: "images/coffee2.jpg" }, { name: "Explicabo", image: "images/coffee3.jpg" }, { name: "Rchitecto", image: "images/coffee4.jpg" }, { name: " Beatae", image: "images/coffee5.jpg" }, { name: " Vitae", image: "images/coffee6.jpg" }, { name: "Inventore", image: "images/coffee7.jpg" }, { name: "Veritatis", image: "images/coffee8.jpg" }, { name: "Accusantium", image: "images/coffee9.jpg" }, ] 

Tad mēs izveidojam karšu masīvu ar nosaukumiem un attēliem.

  • In js/app.js
const showCoffees = () => { let output = "" coffees.forEach( ({ name, image }) => (output += ` 

${name}

Taste `) ) container.innerHTML = output } document.addEventListener("DOMContentLoaded", showCoffees)

With this code above, we can now loop through the array and show them on the HTML file. And to make everything work, we wait until the DOM (Document Object Model) content finishes loading to run the showCoffees method.

We've done a lot, but for now, we just have a traditional web app. So, let's change that in the next section by introducing some PWA features.

super satraukti

Web App Manifest

The web app manifest is a simple JSON file that informs the browser about your web app. It tells how it should behave when installed on the user's mobile device or desktop. And to show the Add to Home Screen prompt, the web app manifest is required.

Now that we know what a web manifest is, let's create a new file named manifest.json (you have to name it like that) in the root directory. Then add this code block below.

  • In manifest.json
{ "name": "Dev'Coffee", "short_name": "DevCoffee", "start_url": "index.html", "display": "standalone", "background_color": "#fdfdfd", "theme_color": "#db4938", "orientation": "portrait-primary", "icons": [ { "src": "/images/icons/icon-72x72.png", "type": "image/png", "sizes": "72x72" }, { "src": "/images/icons/icon-96x96.png", "type": "image/png", "sizes": "96x96" }, { "src": "/images/icons/icon-128x128.png", "type": "image/png","sizes": "128x128" }, { "src": "/images/icons/icon-144x144.png", "type": "image/png", "sizes": "144x144" }, { "src": "/images/icons/icon-152x152.png", "type": "image/png", "sizes": "152x152" }, { "src": "/images/icons/icon-192x192.png", "type": "image/png", "sizes": "192x192" }, { "src": "/images/icons/icon-384x384.png", "type": "image/png", "sizes": "384x384" }, { "src": "/images/icons/icon-512x512.png", "type": "image/png", "sizes": "512x512" } ] } 

In the end, it's just a JSON file with some mandatory and optional properties.

name: When the browser launches the splash screen, it will be the name displayed on the screen.

short_name: It will be the name displayed underneath your app shortcut on the home screen.

start_url: It will be the page shown to the user when your app is open.

display: It tells the browser how to display the app. There are several modes like minimal-ui, fullscreen, browser etc. Here, we use the standalone mode to hide everything related to the browser.

background_color: When the browser launches the splash screen, it will be the background of the screen.

theme_color: It will be the background color of the status bar when we open the app.

orientation: It tells the browser the orientation to have when displaying the app.

icons: When the browser launches the splash screen, it will be the icon displayed on the screen. Here, I used all sizes to fit any device's preferred icon. But you can just use one or two. It's up to you.

Now that we have a web app manifest, let's add it to the HTML file.

  • In index.html (head tag)

As you can see, we linked our manifest.json file to the head tag. And add some other links which handle the iOS support to show the icons and colorize the status bar with our theme color.

With that, we can now dive into the final part and introduce the service worker.

What is a Service Worker?

Notice that PWAs run only on https because the service worker can access the request and handle it. Therefore security is required.

A service worker is a script that your browser runs in the background in a separate thread. That means it runs in a different place and is completely separate from your web page. That's the reason why it can't manipulate your DOM element.

However, it's super powerful. The service worker can intercept and handle network requests, manage the cache to enable offline support or send push notifications to your users.

wow

S0 let's create our very first service worker in the root folder and name it serviceWorker.js (the name is up to you). But you have to put it in the root so that you don't limit its scope to one folder.

Cache the assets

  • In serviceWorker.js
const staticDevCoffee = "dev-coffee-site-v1" const assets = [ "/", "/index.html", "/css/style.css", "/js/app.js", "/images/coffee1.jpg", "/images/coffee2.jpg", "/images/coffee3.jpg", "/images/coffee4.jpg", "/images/coffee5.jpg", "/images/coffee6.jpg", "/images/coffee7.jpg", "/images/coffee8.jpg", "/images/coffee9.jpg", ] self.addEventListener("install", installEvent => { installEvent.waitUntil( caches.open(staticDevCoffee).then(cache => { cache.addAll(assets) }) ) }) 

This code looks intimidating first but it just JavaScript (so don't worry).

We declare the name of our cache staticDevCoffee and the assets to store in the cache. And to perform that action, we need to attach a listener to self.

self is the service worker itself. It enables us to listen to life cycle events and do something in return.

The service worker has several life cycles, and one of them is the install event. It runs when a service worker is installed. It's triggered as soon as the worker executes, and it's only called once per service worker.

When the install event is fired, we run the callback which gives us access to the event object.

Caching something on the browser can take some time to finish because it's asynchronous.

So to handle it, we need to use waitUntil() which, as you might guess, waits for the action to finish.

Once the cache API is ready, we can run the open() method and create our cache by passing its name as an argument to caches.open(staticDevCoffee).

Then it returns a promise, which helps us store our assets in the cache with cache.addAll(assets).

attēlu kešatmiņa

Hopefully, you're still with me.

izmisis

Now, we've successfully cached our assets in the browser. And the next time we load the page, the service worker will handle the request and fetch the cache if we are offline.

So, let's fetch our cache.

Fetch the assets

  • In serviceWorker.js
self.addEventListener("fetch", fetchEvent => { fetchEvent.respondWith( caches.match(fetchEvent.request).then(res =>  return res ) ) }) 

Here, we use the fetch event to, well, get back our data. The callback gives us access to fetchEvent. Then we attach respondWith() to prevent the browser's default response. Instead it returns a promise because the fetch action can take time to finish.

And once the cache ready, we apply the caches.match(fetchEvent.request). It will check if something in the cache matches fetchEvent.request. By the way, fetchEvent.request is just our array of assets.

Then, it returns a promise. And finally, we can return the result if it exists or the initial fetch if not.

Now, our assets can be cached and fetched by the service worker which increases the load time of our images quite a bit.

And most important, it makes our app available in offline mode.

But a service worker alone can't do the job. We need to register it in our project.

daru-daru

Register the Service Worker

  • In js/app.js
if ("serviceWorker" in navigator) { window.addEventListener("load", function() { navigator.serviceWorker .register("/serviceWorker.js") .then(res => console.log("service worker registered")) .catch(err => console.log("service worker not registered", err)) }) } 

Here, we start by checking if the serviceWorker is supported by the current browser (as it's still not supported by all browsers).

Then, we listen to the page load event to register our service worker by passing the name of our file serviceWorker.js to navigator.serviceWorker.register() as a parameter to register our worker.

With this update, we have now transformed our regular web app to a PWA.

mēs to izdarījām

Final thoughts

Throughout this article, we have seen how amazing PWAs can be. By adding a web app manifest file and a service worker, it really improves the user experience of our traditional web app. This is because PWAs are fast, secure, reliable, and – most importantly – they support offline mode.

Many frameworks out there now come with a service worker file already set-up for us. But knowing how to implement it with Vanilla JavaScript can help you understand PWAs.

And you can go even further with service workers by caching assets dynamically or limiting the size of your cache and so on.

Paldies, ka izlasījāt šo rakstu.

Šeit varat to pārbaudīt tiešraidē, un avota kods ir šeit.

Lasiet vairāk manu rakstu savā emuārā

Nākamie soļi

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Apkalpojošā darbinieka dokumentācija

Tīmekļa manifestu ģenerators

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