Kaip sukurti PWA nuo nulio naudojant HTML, CSS ir „JavaScript“

Progresyvios žiniatinklio programos yra būdas perkelti tą savosios programos jausmą į tradicinę žiniatinklio programą. Naudodamiesi „PWA“, mes galime patobulinti savo svetainę naudodami mobiliųjų programų funkcijas, kurios padidina naudojimo galimybes ir suteikia puikią vartotojo patirtį.

Šiame straipsnyje mes sukursime PWA nuo nulio su HTML, CSS ir „JavaScript“. Čia aptarsime temas:

  • Kas yra progresyvioji žiniatinklio programa?
  • Antraštė
  • Stilius
  • Rodyti duomenis su „JavaScript“
  • Žiniatinklio programų manifestas
  • Kas yra paslaugų darbuotojas?
  • Išsaugokite turtą talpykloje
  • Gaukite turtą
  • Užregistruokite aptarnavimo darbuotoją
  • Paskutinės mintys
  • Tolesni žingsniai

Taigi, pradėkime nuo svarbaus klausimo: kas gi yra PWA?

Kas yra progresyvioji žiniatinklio programa?

„Progressive Web App“ yra žiniatinklio programa, teikianti vartotojams panašią į programą patirtį, naudojant šiuolaikines žiniatinklio galimybes. Galų gale, tai tik jūsų įprasta svetainė, veikianti naršyklėje su tam tikrais patobulinimais. Tai suteikia jums galimybę:

  • Norėdami jį įdiegti mobiliajame pagrindiniame ekrane
  • Norėdami jį pasiekti neprisijungę
  • Norėdami pasiekti fotoaparatą
  • Norėdami gauti tiesioginius pranešimus
  • Norėdami atlikti fono sinchronizavimą

Ir dar daugiau.

Tačiau, norėdami paversti savo tradicinę žiniatinklio programą PWA, turime ją šiek tiek pakoreguoti pridėdami žiniatinklio programos aprašo failą ir paslaugų darbuotoją.

Nesijaudinkite dėl šių naujų sąlygų - jas aptarsime toliau.

Pirmiausia turime sukurti savo tradicinę žiniatinklio programą. Taigi pradėkime nuo žymėjimo.

Antraštė

HTML failas yra gana paprastas. Viską suvyniojame į mainžymę.

  • Į index.html
       Dev'Coffee PWA     

Dev'Coffee

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Ir sukurkite naršymo juostą su navžyma. Tada, divsu klase .container, laikys mūsų korteles, kurias vėliau pridėsime naudodami „JavaScript“.

Dabar, kai mes to išvengėme, sukurkime tai su CSS.

Stilius

Čia, kaip įprasta, mes pradedame importuoti mums reikalingus šriftus. Tada atliksime keletą nustatymų iš naujo, kad išvengtume numatytojo elgesio.

  • Į 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; } 

Tada apribojame didžiausią mainelemento plotį 900px, kad jis gerai atrodytų dideliame ekrane.

Naršymo juostai noriu, kad logotipas būtų kairėje, o nuorodos - dešinėje. Taigi, navžymę, padarę ją lanksčią talpyklą, naudojame justify-content: space-between;joms sulyginti.

  • Į 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; } 

Turėsime kelias korteles, todėl konteinerio elementui jis bus rodomas kaip tinklelis. Dabar grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr))mes galime padaryti mūsų korteles reaguojančias, kad jos turėtų bent 15remplotį, jei yra pakankamai vietos (ir 1frjei ne).

Kad jie atrodytų gražiai, mes padvigubiname šešėlio efektą .cardklasėje ir naudojame object-fit: cover, .card--avatarkad vaizdas netemptų.

Dabar atrodo kur kas geriau, bet duomenų vis tiek neturime.

Ištaisykime kitame skyriuje

Rodyti duomenis su „JavaScript“

Atkreipkite dėmesį, kad naudojau didelius vaizdus, ​​kuriuos įkelti reikia šiek tiek laiko. Tai jums geriausiai parodys aptarnaujančių darbuotojų galią.

Kaip sakiau anksčiau, .containerklasė laikys mūsų kortas. Todėl turime jį pasirinkti.

  • Į 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" }, ] 

Tada sukuriame kortelių su vardais ir vaizdais masyvą.

  • Į 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 jaudulys

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.

Oho

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).

vaizdo talpykla

Hopefully, you're still with me.

beviltiška

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.

leisk-daryk

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.

mes tai padarėme

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.

Dėkojame, kad perskaitėte šį straipsnį.

Čia galite tiesiogiai pamatyti, o šaltinio kodas yra čia.

Skaitykite daugiau mano straipsnių savo tinklaraštyje

Tolesni žingsniai

Žiniatinklio manifesto dokumentacija

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