Javascript

Building Mobile Applications with Svelte and NativeScript

Published Oct 17, 2022

Updated Feb 13, 2023

5 min read

This article was written over 18 months ago and may contain information that is out of date. Some content may be relevant but please refer to the relevant official documentation or available resources for the latest information.

Have you ever wanted to build a mobile application using a language you already know?

In this tutorial, we'll learn how to start building a mobile application using Svelte and NativeScript.

What is NativeScript

NativeScript is a framework that will allow you to write Native apps using JavaScript or Typescript and, at the same time, it allows you to access platform-specific Native APIs.

Setting up your environment

The very first step to developing with NativeScript is installing all the required dependencies. If you're lucky, you'll already have everything installed. But if not, we'll see how to get it to work.

The first thing (assuming you already have Node installed) is to install NativeScript globally.

npm i -g nativescript

For this tutorial, I'll be developing an iOS application.

The best way to check if your environment is prepared is to use the command provided by NativeScript.

ns doctor ios

There's an equivalent command for android if that's your target OS.

If you are missing anything, you'll get a bunch of messages with the requirements needed.

In my case, I had to install XCode, Ruby, Some Gems, and Python libraries. Please refer to the setup guide to check what you need (macOS + iOS, for me).

It's important to have your environment ready. Otherwise, we will not be able to run our project.

✔ Getting environment information

No issues were detected.
✔ Xcode is installed and is configured properly.
✔ xcodeproj is installed and is configured properly.
✔ CocoaPods are installed.
✔ CocoaPods update is not required.
✔ CocoaPods are configured properly.
✔ Your current CocoaPods version is newer than 1.0.0.
✔ Python installed and configured correctly.
✔ The Python 'six' package is found.
✔ Xcode version 13.4.1 satisfies minimum required version 10.
✔ Getting NativeScript components versions information...
✔ Component nativescript has 8.3.2 version and is up to date.
✔ Component @nativescript/core has 8.3.2 version and is up to date.
✔ Component @nativescript/ios has 8.3.2 version and is up to date.

Starting a new project

Now that our environment is set up, let's start a new project. We are going to base this example app on this sample from the NativeScript samples page. However, we will add more to it, like including HTTP requests, and a List/Detail navigation.

ns create sveltapp --svelte
✔ Do you want to help us improve NativeScript by automatically sending anonymous usage statistics? We will not use this information to identify or contact you. … no

The command will create a Svelte + NativeScript project, and install the required dependencies.

Our folder structure will look like this:

We'll be focusing on the /app folder where our JS/TS will be added.

<!-- components/Home.svelte -->
<page>
    <actionBar title="Home" />
    <gridLayout>
        <label class="info">
            <formattedString>
                <span class="fas" text="&#xf135;" />
                <span text=" {message}" />
            </formattedString>
        </label>
    </gridLayout>
</page>

<script lang="ts">
    let message: string = "Blank Svelte Native App"
</script>

<style>
    .info .fas {
        color: #3A53FF;
    }

    .info {
        font-size: 20;
        horizontal-align: center;
        vertical-align: center;
    }
</style>

<!-- App.svelte -->
<frame>
    <Home />
</frame>

<script lang="ts">
    import Home from './components/Home.svelte'
</script>

App.svelte will render the default page Home which contains a message and an icon.

You'll notice that these are not the HTML tags you're used to, and that's because these are not HTML elements. These are native elements/views. So if you were thinking of reusing your code in a web app, for example, this is not the part that you'll be able to share.

If that's what you need, make sure you extract the pieces that can be reused.

Building Our Application

Let's delete the content from Home.svelte, and let's talk about what we'll be building.

The app we will build will display a list of items, and when clicked, will navigate into a detailed view. The date for this example will be fetched from the PokeAPI.

Creating a List view

Let´s create our Home page a.k.a the list.

But first, let's create some types to be used in our list.

export type PokemonListApiResponse = {
    count: number,
    next: string | null,
    previous: string | null
    results: Array<{
        name: string,
        url: string
    }>
}

export type PokemonListItem = {
    name: string,
    image: string
}

First, we created a type for the rest API response. It will contain a list of Pokémon with a few properties. We also create a type for the model used in our view.

<script lang="ts">
 import { Template } from "svelte-native/components";
 import { PokemonListItem } from "~/types/pokemon";

 let data: PokemonListItem[] = [];

</script>

<page>
 <actionBar title="pokeAPI" />
 <stackLayout height="100%">
   <listView height="100%" items={data}>
     <Template let:item>
       <gridLayout rows="*" columns="auto, *" margin="5 10" padding="0">
         <image row="0" col="0" src={item.image} class="thumb" />
         <label row="0" col="1" text={item.name} />
       </gridLayout>
     </Template>
   </listView>
 </stackLayout>
</page>

Our page consists of a set of layouts and a list view.

Each list item will display an image and a label.

However, our view is missing data.

Integrating with PokeAPI

Let's create a service that will fetch a list of Pokémon.

// services/api.ts
import { Http } from "@nativescript/core";
import { PokemonListApiResponse, PokemonListItem } from "~/types/pokemon";

export const catchemAll = (limit = 100, offest = 0) =>
  Http.getJSON<PokemonListApiResponse>(
    `https://pokeapi.co/api/v2/pokemon?limit=100&offset=0`
  ).then(
    (res) => {
      return res.results.map((pokemon) => {
        let splitUrl = pokemon.url.split("/");
        let id = splitUrl[splitUrl.length - 2];

        return {
          ...pokemon,
          image: `https://raw.githubusercontent.com/PokeAPI/sprites/master/sprites/pokemon/${id}.png`,
        } as PokemonListItem;
      });
    }
  );

To make a request I'll use the Http API provided by NativeScript. It contains a set of methods that I recommend you to check out before deciding which one will suit better for your use case.

I'm making a little transformation to the received data, to build the URL with the sprite of each item.

Once our service is in place, we'll fetch data and display it.

By default, we will fetch 100 items starting from the first one.

I'll make a request once the item is mounted, which means I'll first render the action bar only, and when the response is received, the list will be rendered.

<script lang="ts">
  import { Template } from "svelte-native/components";
  import { onMount } from "svelte";
  import * as api from "../services/api";
  import { PokemonListItem } from "~/types/pokemon";

  let data: PokemonListItem[] = [];

  onMount(() => {
    api.catchemAll().then((items) => (data = items));
  });

</script>

<page>
  <actionBar title="pokeAPI" />
  <stackLayout height="100%">
    <listView height="100%" items={data} on:itemTap={handleTap}>
      <Template let:item>
        <gridLayout rows="*" columns="auto, *" margin="5 10" padding="0">
          <image row="0" col="0" src={item.image} class="thumb" />
          <label row="0" col="1" text={item.name} />
        </gridLayout>
      </Template>
    </listView>
  </stackLayout>
</page>

Our app should look this by now Scrolling

Much better!

Adding the Details view

For our sample application to be complete, we want to be able to navigate to a more detailed page of a Pokémon when one list item is selected.

First, we need to create our destination component: a detailed view of a Pokémon.

We will be adding fetching a description for the Pokémon, but there's a lot of information you can get from the API.

Let's add this call to the API service, and create our detailed view.

// services/api.ts
// ... other methods
export const getDescription = (id: number) => Http.getJSON(`https://pokeapi.co/api/v2/characteristic/${id}`).then(
  (result: any) => {
    let desc = result.descriptions.find(
      (description: any) => description?.language?.name == "en"
    );
    return desc?.description
  },
);

<!-- components/Details.svelte -->
<script lang="ts">
  import { onMount } from "svelte";
  import * as api from "../services/api";

  export let index: number;
  export let item: any;
  let description = "";

  onMount(() => {
    api.getDescription(index + 1).then(
      (res) => {
        description = res || "No description";
      },
      (e) => {
        description = "Error fetching data";
      }
    );
  });
</script>

<page>
  <actionBar title={item.name} class="action-bar" />
  <scrollView>
    <stackLayout>
      <image margin="0" height="250" stretch="aspectFit" src={item.image} />
      <stackLayout padding="10 20">
        <stackLayout>
          <label
            marginTop="15"
            fontSize="16"
            fontWeight="700"
            class="text-primary"
            textWrap="true"
            text="Description"
          />
          <label
            fontSize="14"
            class="text-secondary"
            textWrap="true"
            text={description || "Loading..."}
          />
        </stackLayout>
      </stackLayout>
    </stackLayout>
  </scrollView>
</page>

We will be using a set of stackLayout to build our view, display the image, add the name to the action bar, and finally show a loading message while getting the description, and an error if it fails.

Notice there are two properties exported. This means that these properties must be passed as inputs from a parent.

Bringing all together

It's time to connect the list view, and the details view.

Let's see the final Home Page:

<script lang="ts">
  import { navigate } from "svelte-native";
  import { Template } from "svelte-native/components";
  import { ItemEventData } from "@nativescript/core";
  import { onMount } from "svelte";
  import Details from "./Details.svelte";
  import * as api from "../services/api";
  import { PokemonListItem } from "~/types/pokemon";

  let data: PokemonListItem[] = [];

  onMount(() => {
    api.catchemAll().then((items) => (data = items));
  });

  function handleTap(event: ItemEventData) {
    navigate({
      page: Details,
      props: { index: event.index, item: data[event.index] },
    });
  }
</script>

<page>
  <actionBar title="pokeAPI" />
  <stackLayout height="100%">
    <listView height="100%" items={data} on:itemTap={handleTap}>
      <Template let:item>
        <gridLayout rows="*" columns="auto, *" margin="5 10" padding="0">
          <image row="0" col="0" src={item.image} class="thumb" />
          <label row="0" col="1" text={item.name} />
        </gridLayout>
      </Template>
    </listView>
  </stackLayout>
</page>

We have now included an event listener (on:itemTap), that will then call the navigate method included in svelte-native. Here, we passed the required props item and index to the Details Component.

Now we have connected both views.

We don't have to think about a back button in our details view because it's automatically there when you navigate, and add a view to the navigation stack.

The final result:

Success.

Publishing your app

If you want to publish the application start by running ns prepare ios --release Open the project in XCode and follow the instructions on how to publish an iOS app.

Final words

Being able to work on a native application using a language and a framework you're comfortable with can be a benefit. But there's a cost to it. Setting up the environment is not as straightforward as it could be, but thankfully, the CLI makes it a lot easier to diagnose what's required.

There's a lot more to explore in NativeScript like using plugins, but it's out of scope for this post, where we explore the usage of Svelte with NativeScript. You can check the code from this tutorial in this repo.

This Dot is a consultancy dedicated to guiding companies through their modernization and digital transformation journeys. Specializing in replatforming, modernizing, and launching new initiatives, we stand out by taking true ownership of your engineering projects.

We love helping teams with projects that have missed their deadlines or helping keep your strategic digital initiatives on course. Check out our case studies and our clients that trust us with their engineering.

About the author(s)

Ignacio Falk
I love to learn new things and share what I know. Mentor, Writer, Speaker Member of the local community
@flakolefluk @flakolefluk

Svelte 4 Launch Party Recap

In this Svelte 4 Launch Party event, our panelists discussed the release of Svelte 4. In this wrap-up, we will talk about panel discussions with Svelte core team members, which is an in-depth exploration of the Svelte 4 release, highlighting its key features and performance enhancements. You can watch the full Svelte 4 Launch Party event on the This Dot Media's YouTube channel. Here is a complete list of the host and panelists that participated in this online event: Hosts: - Tracy Lee, CEO, This Dot, @ladyleet - Rob Ocel, Team Lead & Software Architect, This Dot, @robocell Panelists: - Geoff Rich, Svelte Core Team, @geoffrich_ - Simon Holthausen, Full-time Svelte maintainer, @dummdidumm_ - Puru Vijay, Svelte Core Team, @puruvjdev - Benn McCann, SvelteKit Maintainer, @BenjaminMcCann Introductions Geoff, one of the Svelte maintainers, started the introductions. He expressed his excitement about the new major version of Svelte and shared his years of experience using the framework. In his day job, Geoff is a Senior Software Engineer at Ordergroove. Simon, a full-time Svelte maintainer working at Vercel, was busy preparing and finally releasing Svelte 4. He happily noted that there were very few bugs, and everything seemed to be working smoothly. Simon's dedication to maintaining the framework has contributed significantly to its success. Puru, a college student, showcased his impressive skills by working on the website and the REPL for Svelte. Balancing his studies with web development, Puru demonstrated his passion for Svelte and his contributions to its ecosystem. Ben primarily focuses on Svelte Kit, but also pitched in with Svelte 4. Besides his work on Svelte, Ben is an entrepreneur, adding an extra dimension to his diverse skill set. His contributions to the Svelte community have been invaluable. What Should Everyone Be Excited About in Svelte 4? Svelte 4 has arrived, and while it may not be packed with mind-blowing features, there are several neat little improvements that are worth getting excited about. The main focus of this release was on maintenance and cleaning up the framework to pave the way for the big Svelte 5 release. So don't worry, there are bigger things in the pipeline! One of the first things to note is that file sizes in Svelte 4 have significantly decreased by about 10 to 12 fold. This means that your website will load much faster, thanks to the reduced bundle size. Additionally, improvements have been made in hydration, which affects the speed at which pages hydrate. The core around hydration has become smaller, resulting in improved performance. Another noteworthy enhancement in Svelte 4 is the complete overhaul of custom element support. This change, although technically a breaking one, introduces a new wrapper approach. Previously, in Svelte 3, you had to use every Svelte component as a custom element, even if you wanted to keep certain components as internal implementation details. With the wrapper approach, you now have the flexibility to use components as regular Svelte components internally, fixing a range of bugs and fulfilling numerous feature requests. This change proved to be a tremendous success, resolving multiple issues in one fell swoop. Svelte 4 brings value to your day-to-day development experience. For example, the improved type generation and autocomplete have made working with Svelte components a lot smoother. The autocomplete feature now grabs the correct import, eliminating the frustrations of navigating to the wrong files. Additionally, the introduction of declaration maps allows you to see the actual source code, providing a better understanding of the inner workings of Svelte. There's also good news for those who want to contribute to the Svelte codebase. In Svelte 4, the entire codebase has been converted from TypeScript to JavaScript with JS Docs. While type checking is still in place to ensure error-free development, this change simplifies the process of working with the source code. Developers can now directly edit the source and test changes without worrying about the mapping between TypeScript and JavaScript. In terms of performance, the reduction in bundle sizes has made a significant impact. Although the size reduction percentage may have been misunderstood by some, primarily referring to the compiler size rather than the runtime bundle, it has tangible benefits in scenarios like online tutorials and interactive experiences. Beyond the technical improvements, Svelte 4 also brings updates to the documentation site and the main website. The team has put in considerable effort to enhance the user experience, making it easier to navigate and find the information you need. Puru Does a Run Through of the Updates to the Svelte.dev Site Puru shares exciting news to share about the overhaul of the svelte.dev website. First things first, let's talk about the star of the show: dark mode. It's finally here, and it's a game-changer. They’ve given the entire site a fresh redesign, taking inspiration from the sleek look of kit.svelte.dev. You'll notice some similarities, but they’ve added their own unique touch to make it shine. They’re now linking to the improved tutorial on learn.svelte.dev, which is definitely worth checking out. Now, let's dive into the docs. They've made some significant changes to make your browsing experience a breeze. Instead of a single page, they've divided everything into multiple pages, making it super easy to find what you're looking for. Each component, logic block, and style module has its own dedicated page. It's all organized and up-to-date, thanks to the auto-generation from the source code. Say goodbye to outdated information and hello to hassle-free browsing. They've introduced some fantastic new features that you're going to love. In the REPL, they've added multiple cursors, making coding even more efficient. Plus, they've created a REPL User Guide, packed with handy shortcuts and nifty tips and tricks. And here's the best part: our code snippets now support TypeScript. Just a simple click, and you'll have the TypeScript equivalent at your fingertips. It couldn't get any easier to level up your coding game! So, head over to the new website, immerse yourself in the revamped docs, and enjoy all the fantastic updates we've made. And don't forget to check out the blog section for more in-depth information. Happy browsing, and get ready to experience the best of the new and improved website! Upgrading from Svelte 3 to Svelte 4 Well there are a few things you need to know. But don't worry, it's not too complicated. First off, you'll find all the breaking changes highlighted and summarized on the migration Doc Page. So, if something breaks, you can check it out there. If you're still on Svelte 3, the best way to start is by using the migration script. Just type in npx svelte-migrate svelte-4 in your command line, and it will go through your code base and automatically update things like tightened up types and local transitions. The migration script will even ask you if you want to migrate your global transitions or not. It's like a little questionnaire to make sure everything goes smoothly. The migration script does a lot of the heavy lifting for you, updating dependencies in your package.json and ensuring peer dependency versions match up. It takes care of most things, but there might be a few other changes you'll need to handle. That's where the migration guide comes in handy. It covers all the other changes and helps you navigate through them. Now keep in mind that upgrading to Svelte 4 might require at least Node 16. So, if you're using older dependencies that are holding you back from upgrading Node, it's time to poke your manager or tech lead and emphasize the need to stay current. After all, using outdated versions can pose security vulnerabilities. So make a strong case for the upgrade and let them know it's time to invest in keeping things up to date. Geoff talked about how he has already upgraded a few sites to Svelte 4, and honestly, just upgraded the dependencies, and it worked like a charm. He didn't even bother running the migration script himself. Different projects may have different needs, so it's always good to be aware of any potential obstacles. Stay up to date and remember, keeping things secure is a top priority! Svelte 4 and How It Works with Svelte Kit If you're using Svelte Kit and thinking about upgrading to Svelte 4, here's what you need to know. The good news is that you can stick with your current version of Svelte Kit if you want, but there will be a warning about the peer dependencies not matching up. We made a small change to officially support Svelte 4 within Svelte Kit. But other than that, not much else has changed. One important thing to remember is to upgrade the plugins file that Svelte Kit uses. You can do this by updating your lock file or simply upgrading to the latest Svelte Kit, which will take care of it for you. The migration script handles all the necessary updates, so running it will ensure everything works smoothly. When it comes to impact, Svelte 4 brings some improvements. Your hydration code will be smaller, and the hydration speed will be faster, which means your final app bundle could be around 10% smaller. We've been working on even more performance enhancements, and using the Chrome performance tab in the developer tools can help you identify areas that need improvement. So, in a nutshell, upgrading to Svelte 4 is optional for Svelte Kit users. But, it brings benefits like smaller code and faster hydration. Just remember to update the plugins file and use the migration script to handle any necessary changes. Keep an eye on the Chrome performance tab for optimization opportunities. Are Svelte and Svelte Kit Going to be Paired in the Future in Updates or Stay Independent? When it comes to updates for Svelte and Svelte Kit, there's a relationship between the two, but they also have their own focuses. The development of Svelte and Svelte Kit is somewhat interconnected, with learnings and improvements transferring between them. While the maintainers tend to focus on one major project at a time to gather feedback and make meaningful changes, they do draw lessons from both and apply them accordingly. For example, the decision to make transitions local by default in Svelte 4 stemmed from insights gained during the development of Svelte Kit. Although there may be periods of emphasis on either Svelte or Svelte Kit, they are designed to complement each other and take advantage of each other's features. The development teams work on both code bases, ensuring a coordinated approach. While there may be a Svelte Kit 2 in the future, it's important to note that the release of Svelte 5 doesn't automatically mean a corresponding major update for Svelte Kit. The decision to introduce a new version depends on various factors, such as API changes and compatibility with the latest versions of Svelte, Node.js, and bundlers. Ultimately, the goal is to provide a seamless and optimized experience for developers using Svelte and Svelte Kit. By developing them in tandem and leveraging the benefits of each, the teams behind these projects ensure continuous improvements and adaptability to the evolving needs of the community. Svelte Dev Tools Repo and Funding for Svelte So, regarding the Svelte Dev Tools repo, it used to be a community-maintained project led by a contributor named Red Hatter. She developed and published it independently. But more recently, she transferred the repository to the Svelte team so that they could also contribute and provide support. Currently, the team hasn't been able to publish new versions of the extension to the store, so there might still be the Svelte 3 version available. However, they are working on publishing a new version and may ask users to switch over to it for Svelte 4. Now, let's talk about funding for Svelte. While financial support is definitely appreciated, the team also values something equally important—time. Companies can make a significant impact by allowing their employees to work on Svelte or Svelte Kit, fixing bugs, and contributing their time and expertise to improving the projects. Donations are welcome, of course, but finding skilled developers like Pooria (one of the Svelte team members) can be challenging even with funding available. So, giving employees the time and freedom to work on Svelte-related projects is highly appreciated and can have a significant positive impact. It's not just about money; it's about investing resources, whether financial or human, into the growth and development of the Svelte community. Getting Involved in Open Source If you're interested in getting involved in open source for Svelte, the journey can take different paths. One way to start is by creating projects or contributing to existing ones in the Svelte ecosystem. For example, Peru mentioned that he initially created a Svelte version of a tool called MacOS, which gained attention and led to him becoming a Svelte ambassador. Being active in the community, showcasing your work, and advocating for Svelte through speaking engagements or participating in events like Svelte Summit can also help raise your profile. Becoming a Svelte ambassador or being recognized by the core team doesn't necessarily require direct contributions to the Svelte codebase. You can contribute in various ways, such as creating engaging content like videos or blog posts that benefit the community, maintaining popular Svelte libraries, assisting users on platforms like Discord or Stack Overflow, and participating in GitHub discussions. The core team and community value not only code contributions but also the positive impact and dedication you bring to the Svelte community. It's worth noting that the journey can be unique for each person. Even if you haven't contributed to the Svelte codebase directly, like the ambassadors Hunter Byte and Joy of Code, you can still make a significant impact and be recognized for your contributions. For instance, Pooria mentioned that his first contribution was focused on creating the Svelte website rather than working on the core Svelte codebase. So, anyone with a passion for Svelte and a willingness to contribute can become a Svelte ambassador and actively participate in the open-source community. Contributing to Open Source Contributing to open-source projects like Svelte may seem daunting, but you don't have to understand the entire codebase from the start. Start by looking for beginner-friendly issues labeled as "good first issue" or similar tags. These provide a starting point to dive into the codebase. Follow the code path, use failing tests as guidance, and utilize features like control-clicking to navigate to relevant implementations. Documentation and contribution guides are valuable resources for newcomers. Svelte Kit, for instance, has focused on making its codebase beginner-friendly. If you encounter difficulties, join the project's Discord channel and seek guidance from experienced contributors. Providing feedback on areas where more documentation is needed can help improve the contributor experience. You can also contribute to adjacent tools related to Svelte, such as Prettier or ESLint plugins, which are maintained by the core team. These projects are often smaller in size and provide a manageable entry point. Additionally, non-coding contributions like improving project workflows or setting up testing and CI processes are also valuable. Remember that contributions, regardless of their scale, have a positive impact on the project and the open-source community. Focus on understanding the specific area you want to work on, leverage available resources, engage with the community, and consider contributing to adjacent projects. With these steps, you can jump into contributing to open source and start making a difference. Closing Thoughts from Panelists Simon shared his enthusiasm for the future of Svelte, particularly the highly anticipated Svelte 5. The recent addition of Dominic to the team has already made a significant impact, and the brainstorming sessions have been rewarding. Exciting things are on the horizon for Svelte users. Geoff encouraged everyone to give Svelte 4 a try and welcomes feedback and issue reports as they continue to refine and improve the framework. He emphasized that they are still in the early stages after the release and appreciate the community's support in upgrading their apps and providing valuable insights. Peru gave a special shout-out to Paulo Ricca, who has been instrumental in resolving issues with the new REPL. With Paulo's assistance, the REPL is now as stable and impressive as before. Peru expresses his gratitude for the collaboration. Ben extended his appreciation to the ecosystem integrations, mentioning the Storybook team and Jesse Beech, who contributed to optimizing file sizes and ensuring Svelte's compatibility with other JavaScript projects. The Svelte team is open to supporting and collaborating with anyone seeking to integrate Svelte with other tools in the ecosystem. Overall, the panelists were thankful, excited about the future, and grateful for the community's contributions and collaborations. The energy and positive feedback drove their motivation, and they encouraged everyone to continue exploring and pushing the boundaries of what Svelte can achieve. Conclusion In this Svelte 4 Launch Party, the panelists express their gratitude to the vibrant Svelte community for their unwavering support and positive energy. The launch of Svelte 4 and the promising developments of Svelte 5 have generated excitement and anticipation among developers. The core team's commitment to continuous improvement, collaboration with ecosystem integrations, and dedication to addressing user feedback are evident. As Svelte evolves, the contributions of individuals, whether through code, documentation, or community engagement, are valued and celebrated. With the momentum and enthusiasm surrounding Svelte, the future looks bright for this innovative framework and its passionate community....

Jun 30, 2023

12 mins

Svelte

Svelte 4: Unveiled Speed Enhancements and Developer-Centric Features

Svelte 4: Unveiled Speed Enhancements and Developer-Centric Features Svelte, a widely favored framework for building user interfaces, unveiled its much-anticipated version 4 on June 22. This major release, while paving the way for future advancements, brings a plethora of remarkable enhancements. Focusing on enriching the development experience and boosting performance, Svelte 4 is indeed reshaping the landscape of frontend development. In this post, we'll delve into the specifics of this exciting release, covering the significant performance boosts, enriched developer tools and features, revamped websites, and simplified migration guide. A Deeper Look at Performance Enhancements Svelte 4 delivers remarkable improvements in performance, focusing on shrinking the Svelte package size, and enhancing hydration efficiency. Streamlined Svelte Package Svelte 4 has substantially slimmed down, reducing its overall package size from 10.6 MB to a sleek 2.8 MB - a 75% decrease. This reduction in dependencies from 61 to 16 not only lightens Svelte but also optimizes SvelteKit, significantly accelerating the REPL experience and npm install times. For instance, npm install times have been trimmed from over 5 minutes to less than a minute, a leap in quality that any developer will appreciate. NPM I Before: NPM I After: Bundle Size Before: Bundle Size After: Optimized Hydration and Performance Scores Alongside the impressive package size reduction, Svelte 4 offers more efficient code hydration, reducing the generated code size for the SvelteKit website by nearly 13%. This leaner codebase contributes to higher performance on benchmarks like Google Lighthouse. The performance score for the new Svelte 4 starter on starter.dev has soared from 75% to a near perfect 95+%. Overall, the performance enhancements introduced with Svelte 4 mean a faster, more efficient, and smoother developer experience. Before: After: Enhanced Developer Experience in Svelte 4 Localized Transitions Transitions in Svelte 4 are local by default, preventing potential conflicts during page loading. ` Improved Web Component Authoring Web Components authoring is simplified with the dedicated customElement attribute in svelte:options. ` Stricter Type Enforcement Svelte 4 introduces stricter types for createEventDispatcher, Action, ActionReturn, and onMount. ` These changes collectively offer a streamlined, robust, and efficient coding experience. Revamped Svelte Websites With Svelte 4, the team has also revamped its main website, offering an improved and more user-friendly experience. The Tutorial Website The Svelte tutorial website has been overhauled for an enhanced learning journey. New improvements include a visible file structure, fewer elements in the navbar, smoother navigation between sections, and a new dark mode. The Svelte Website The primary Svelte website received a makeover too, including better mobile navigation, improved TypeScript documentation, and a handy dark mode. These website updates aim to provide a more engaging, intuitive, and user-friendly experience for all Svelte users. A Smooth Migration to Svelte 4 Transitioning from Svelte 3 to Svelte 4 is designed to be as straightforward as possible. The Svelte team has provided an updated migration tool to simplify this process. Here is a step-by-step guide for the transition: 1. Run the Svelte migration tool. ` 2. Remove Svelte 3 packages. ` 3. Update your eslintrc.json configuration file. ` 4. Upgrade Storybook related packages to the latest v7. Note: as of the publishing of this article, the latest version is 7.0.26. ` Do note that the minimum version requirements have changed. You will now need: - NodeJS 16 or higher - SvelteKit 1.20.4 or higher - TypeScript 5 or higher For more detailed instructions and information, please refer to the official Svelte 4 migration guide or you can take a look at our Svelte 4 starter kit on starter.dev. The focus is to ensure a hassle-free transition, allowing developers to take advantage of the new features and enhancements Svelte 4 offers without significant obstacles. Conclusion Svelte 4, with its performance enhancements and streamlined development process, offers a new pinnacle in the realm of JavaScript frameworks. If you're keen on shifting from Svelte 3 to Svelte 4, a comprehensive migration guide is provided to facilitate a smooth transition. For a quick start with Svelte 4, check out our ready-to-use Svelte Kit with SCSS Starter Kit. In addition, we've developed two showcases demonstrating Svelte 4's power: 1. Svelte Kit with SCSS & 7GUIs - A comprehensive demo showcasing various UI challenges. 2. GitHub Replica Showcase - A clone of the popular code hosting platform, GitHub, demonstrating the potential of Svelte 4 in building complex and high-performance web applications. In conclusion, Svelte 4 brings numerous performance improvements and enriches the development experience, thereby increasing developer productivity and enabling the creation of more efficient applications. Its thoughtful design, alongside the streamlined migration process, is set to expand its adoption in the web development community....

Jul 26, 2023

5 mins

Svelte

Svelte 5 is Here!

Svelte 5 was finally released after a long time in development. Fortunately, we've been able to test it for some time, and now it has a stable release. Let's dig into its features and why this is such a significant change, even though Svelte 4 code is almost 100% compatible. Svelte syntax everywhere This is one of my favorite additions. Previously, Svelte syntax was limited to a component element. Refactoring code from a component and moving it to a JavaScript file worked differently. Now you can use the .svelte.js or .svelte.ts extension, which allows you to use the same syntax everywhere. It's important to note that it's a way to express that this is not just JS, and what you write may be compiled to something else, just like .svelte files are not just html even though they look very similar. Runes The introduction of runes is one of the most significant changes in Svelte. Many users felt attracted to variables being instantly reactive in previous versions. ` There was, however, a lot of magic underneath and a considerable amount of work from the compiler to make it behave reactively. $state In Svelte 5, a reactive variable has to be explicitly declared using the $state rune, which brings a clear distinction between what is reactive and what isn’t. ` In the previous code, $state is not an actual function being called; it's a hint for the compiler to do something special with this declaration. Rune names always start with a dollar sign ($) and do not need to be imported. However, there’s much more to the changes than just the way we declare reactive variables. Runes bring a lot of new features that make Svelte 5 a great improvement. In Svelte 5, objects or arrays use Proxies to allow for granular reactivity, meaning that individual properties in an object are reactive, even if they are nested objects or arrays. If you modify a property, it will only update that property and will not trigger an update on the whole object. It also supports triggering updates when methods like array.push are called. In previous versions, an assignment was required to trigger an update: ` To have a similar behavior of svelte 4 (no deep reactivity), use the $state.raw() rune. This syntax of .* is common for related features of a rune: $state.raw() will require an assignment to trigger reactivity. ` Because proxies are used, you may need to extract the underlying state instead of the proxy itself. In that case, $state.snapshot() should be used: ` $derived We will use $derived and $derived.by to declare a derived state. The two runes are essentially the same, except one allows us to use a function instead of an expression, allowing for more complex operations to calculate the derived values. ` $effect Effects are useful for running something triggered by a change in state. One of the things you'll note from the $effect rune is that dependencies don't need to be explicit. Those will be picked from reactive values read synchronously in the body of the effect function. ` Something to bear in mind is that these dependencies are picked each time the effect runs. The values read during the last run become the dependencies of the effect. ` Depending on the result of the random method, foo or bar will stop being a dependency of the effect. You should place them outside the condition so they can trigger reruns of the effect. *Variants* of the effect rune are $effect.pre, which runs before a DOM update, and $effect.tracking(), which checks for the context of the effect (true for an effect inside an effect or in the template). $props This rune replaces the export let keywords used in previous versions to define a component's props. To use the $props syntax, we can consider it to return an object with all the properties a component receives. We can use JavaScript syntax to destructure it or use the rest property if we want to retrieve every property not explicitly destructured.. ` $bindable If you want to mutate a prop so that the change flows back to the parent, you can use the $bindable prop to make it work in both directions. A parent component can pass a value to a child component, and the child component is able to modify it, returning the data back to the parent component. ` $inspect The $inspect rune only works in dev mode and will track dependencies deeply. By default, it will call console.log with the provided argument whenever it detects a change. To change the underlying function, use $inspect.with().with): ` $host The host rune gives access to the host element when compiling as a custom element: ` ` Other changes Another important change is that component events are just props in Svelte 5, so you can destructure them using the $props() rune: ` A special children property can be used to project content into a component instead of using slots. Inside the components, use the [@render[(https://svelte.dev/docs/svelte/@render) tag to place them. ` Optional chaining (?.) prevents from attempting to render it if no children are passed in. If you need to render different components in different places (named slots before Svelte 5, you can pass them as any other prop, and use @render with them. Snippets Snippets allow us to declare markup slices and render them conveniently using the render tag (@render). They can take any number of arguments. ` Snippets can also be passed as props to other components. ` ` Conclusion Some exciting changes to the Svelte syntax were introduced while, at the same time, maximum compatibility efforts were made. This was a massive rewrite with numerous improvements in terms of performance, bundle size, and DX. Besides that, a new CLI has been released, making the whole experience of starting a project or adding features delightful. If you haven't tried Svelte before, it's a great time to try it now....

Nov 27, 2024

4 mins

Svelte

Introduction to Zod for Data Validation

As web developers, we're often working with data from external sources like APIs we don't control or user inputs submitted to our backends. We can't always rely on this data to take the form we expect, and we can encounter unexpected errors when it deviates from expectations. But with the Zod library, we can define what our data ought to look like and parse the incoming data against those defined schemas. This lets us work with that data confidently, or to quickly throw an error when it isn't correct. Why use Zod? TypeScript is great for letting us define the shape of our data in our code. It helps us write more correct code the first time around by warning us if we are doing something we shouldn't. But TypeScript can't do everything for us. For example, we can define a variable as a string or a number, but we can't say "a string that starts with user_id_ and is 20 characters long" or "an integer between 1 and 5". There are limits to how much TypeScript can narrow down our data for us. Also, TypeScript is a tool for us developers. When we compile our code, our types are not available to the vanilla JavaScript. JavaScript can't validate that the data we actually use in our code matches what we thought we'd get when we wrote our TypeScript types unless you're willing to manually write code to perform those checks. This is where we can reach for a tool like Zod. With Zod, we can write data schemas. These schemas, in the simplest scenarios, look very much like TypeScript types. But we can do more with Zod than we can with TypeScript alone. Zod schemas let us create additional rules for data parsing and validation. A 20-character string that starts with user_id_? It's z.string().startsWith('user_id_').length(20). An integer between 1 and 5 inclusive? It's z.number().int().gte(1).lte(5). Zod's primitives give us many extra functions to be more specific about *exactly* what data we expect. Unlike TypeScript, Zod schemas aren't removed on compilation to JavaScript—we still have access to them! If our app receives some data, we can verify that it matches the expected shape by passing it to your Zod schema's parse function. You'll either get back your data in exactly the shape you defined in your schema, or Zod will give you an error to tell you what was wrong. Zod schemas aren't a replacement for TypeScript; rather, they are an excellent complement. Once we've defined our Zod schema, it's simple to derive a TypeScript type from it and to use that type as we normally would. But when we really need to be sure our data conforms to the schema, we can always parse the data with our schema for that extra confidence. Defining Data Schemas Zod schemas are the variables that define our expectations for the shape of our data, validate those expectations, and transform the data if necessary to match our desired shape. It's easy to start with simple schemas, and to add complexity as required. Zod provides different functions that represent data structures and related validation options, which can be combined to create larger schemas. In many cases, you'll probably be building a schema for a data object with properties of some primitive type. For example, here's a schema that would validate a JavaScript object representing an order for a pizza: ` Zod provides a number of primitives for defining schemas that line up with JavaScript primitives: string, number, bigint, boolean, date, symbol, undefined, and null. It also includes primitives void, any, unknown, and never for additional typing information. In addition to basic primitives, Zod can define object, array, and other native data structure schemas, as well as schemas for data structures not natively part of JavaScript like tuple and enum. The documentation contains considerable detail on the available data structures and how to use them. Parsing and Validating Data with Schemas With Zod schemas, you're not only telling your program what data should look like; you're also creating the tools to easily verify that the incoming data matches the schema definitions. This is where Zod really shines, as it greatly simplifies the process of validating data like user inputs or third party API responses. Let's say you're writing a website form to register new users. At a minimum, you'll need to make sure the new user's email address is a valid email address. For a password, we'll ask for something at least 8 characters long and including one letter, one number, and one special character. (Yes, this is not really the best way to write strong passwords; but for the sake of showing off how Zod works, we're going with it.) We'll also ask the user to confirm their password by typing it twice. First, let's create a Zod schema to model these inputs: ` So far, this schema is pretty basic. It's only making sure that whatever the user types as an email is an email, and it's checking that the password is at least 8 characters long. But it is *not* checking if password and confirmPassword match, nor checking for the complexity requirements. Let's enhance our schema to fix that! ` By adding refine with a custom validation function, we have been able to verify that the passwords match. If they don't, parsing will give us an error to let us know that the data was invalid. We can also chain refine functions to add checks for our password complexity rules: ` Here we've chained multiple refine functions. You could alternatively use superRefine, which gives you even more fine grained control. Now that we've built out our schema and added refinements for extra validation, we can parse some user inputs. Let's see two test cases: one that's bound to fail, and one that will succeed. ` There are two main ways we can use our schema to validate our data: parse and safeParse. The main difference is that parse will throw an error if validation fails, while safeParse will return an object with a success property of either true or false, and either a data property with your parsed data or an error property with the details of a ZodError explaining why the parsing failed. In the case of our example data, userInput2 will parse just fine and return the data for you to use. But userInput1 will create a ZodError listing all of the ways it has failed validation. ` ` We can use these error messages to communicate to the user how they need to fix their form inputs if validation fails. Each error in the list describes the validation failure and gives us a human readable message to go with it. You'll notice that the validation errors for checking for a valid email and for checking password length have a lot of details, but we've got three items at the end of the error list that don't really tell us anything useful: just a custom error of Invalid input. The first is from our refine checking if the passwords match, and the second two are from our refine functions checking for password complexity (numbers and special characters). Let's modify our refine functions so that these errors are useful! We'll add our own error parameters to customize the message we get back and the path to the data that failed validation. ` Now, our error messages from failures in refine are informative! You can figure out which form fields aren't validating from the path, and then display the messages next to form fields to let the user know how to remedy the error. ` By giving our refine checks a custom path and message, we can make better use of the returned errors. In this case, we can highlight specific problem form fields for the user and give them the message about what is wrong. Integrating with TypeScript Integrating Zod with TypeScript is very easy. Using z.infer<typeof YourSchema> will allow you to avoid writing extra TypeScript types that merely reflect the intent of your Zod schemas. You can create a type from any Zod schema like so: ` Using a TypeScript type derived from a Zod schema does *not* give you any extra level of data validation at the type level beyond what TypeScript is capable of. If you create a type from z.string.min(3).max(20), the TypeScript type will still just be string. And when compiled to JavaScript, even that will be gone! That's why you still need to use parse/safeParse on incoming data to validate it before proceeding as if it really does match your requirements. A common pattern with inferring types from Zod schemas is to use the same name for both. Because the schema is a variable, there's no name conflict if the type uses the same name. However, I find that this can lead to confusing situations when trying to import one or the other—my personal preference is to name the Zod schema with Schema at the end to make it clear which is which. Conclusion Zod is an excellent tool for easily and confidently asserting that the data you're working with is exactly the sort of data you were expecting. It gives us the ability to assert at runtime that we've got what we wanted, and allows us to then craft strategies to handle what happens if that data is wrong. Combined with the ability to infer TypeScript types from Zod schemas, it lets us write and run more reliable code with greater confidence....

Nov 15, 2024

7 mins

JavaScriptZod

Let's innovate together!

We're ready to be your trusted technical partners in your digital innovation journey.

Whether it's modernization or custom software solutions, our team of experts can guide you through best practices and how to build scalable, performant software that lasts.

Building Mobile Applications with Svelte and NativeScript

What is NativeScript

Setting up your environment

Starting a new project

Building Our Application

Creating a List view

Integrating with PokeAPI

Adding the Details view

Bringing all together

Publishing your app

Final words

Ignacio Falk

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Let's innovate together!

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Svelte 4 Launch Party Recap

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