Javascript

How to Serve a Single Page Application (SPA) using Rollup.js and Web Dev Server

Published Dec 30, 2020

Updated Feb 14, 2023

6 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This article was written over 18 months ago and may contain information that is out of date.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.

In a previous post, I explained How to setup a TypeScript project using Rollup.js. In that article, I covered the necessary steps to have a Project Setup ready to generate a build using TypeScript and Rollup configurations.

So let's take that project as a starting point to serve a Single-page Application using modern web tools.

What is a SPA (Single-page Application)?

According to MDN Documentation:

An SPA (single-page application) is a web app implementation that loads only a single web document, and then updates the body content of that single document via JavaScript APIs such as XMLHttpRequest and Fetch when different content is to be shown.

A single-page application allows updating only some portions of the current page instead of doing a page refresh. Think about some applications you use every day:

Gmail
Facebook
Twitter
LinkedIn

All of these applications have been built with the user experience in mind along with a good loading speed and navigation between pages.

There are very good reasons to keep building applications following the SPAs approach.

What is Web Dev Server?

Web Dev Server, as its name states, it's a web server for development. It helps development using native browser features like ES modules. It has a plugin architecture for code transformations.

Web Dev Server is the successor of es-dev-server

It's worth mentioning that Web Dev Server allows configuring auto-reload on file changes along with efficient browser caching for faster reloads. It's configurable and supports rollup plugins too!

Project Setup

Prerequisites

You'll need to have installed the following tools in your local environment:

Node.js. Preferably the latest LTS version.
A package manager. You can use either NPM or Yarn. This tutorial will use NPM.

Initialize the Project

Let's create a clone or download the project seed before adding the new configurations and tools:

git clone https://github.com/luixaviles/typescript-rollup.git
cd typescript-rollup/
git checkout tags/01-setup-ts-rollup -b 02-serve-spa

The previous commands will download the project and create a new branch 02-serve-spa to get started.

Source Code Files

Once you have the project ready, open it with your favorite code editor and pay attention to the current project structure:

|- typescript-rollup
    |- src/
        |- math/
            |- math.ts
            |- index.ts
        |- string/
            |- string.ts
            |- index.ts
        |- app.ts
    |- package.json
    |- rollup.config.js
    |- tsconfig.json

Installing Web Dev Server and Concurrently

Let's add some development dependencies to the project.

Install Web Dev Server

npm install --save-dev @web/dev-server

As I mentioned before, Web Sev Server will be the main tool to configure and run our project this time.

Also, if you already know es-dev-server tool, used actively on the Open Web Components initiative, you'll understand that this project migrated to Modern Web website. That does not mean anything other than this new tool continues to be actively developed and can be used in any JavaScript project (TypeScript included ;-)).

Install Concurrently tool

npm install --save-dev concurrently

If you are familiar with any command-line tool, you may have wanted to run commands in parallel.

Concurrently has the same goal. However, it's hard to keep track of every command output and concurrently allows you to run any command you want. It's possible to kill all of them if anyone fails.

TypeScript Configuration

In this case, the tsconfig.json file will remain the same, without any changes:

{
  "compilerOptions": {
    "target": "es2018",                          
    "module": "esnext",
    "moduleResolution": "node",                     
    "noEmitOnError": true,
    "lib": ["es2017"],                            
    "strict": true,  
    "esModuleInterop": false,                 
    "outDir": "out-tsc",
    "rootDir": "./"
  }
  ,
  "include": ["./src/**/*.ts"]
}

Remember, this file is required to be present in the root of any TypeScript project.

Rollup Configuration

The project is configured to use Rollup as the module bundler. It's possible to run it through command-line parameters. However, if you're looking for advanced functionality, you can consider a rollup.config.js file:

import merge from 'deepmerge';
import { createBasicConfig } from '@open-wc/building-rollup';

const baseConfig = createBasicConfig();

export default merge(baseConfig, {
  input: './out-tsc/src/app.js',
  output: {
      dir: 'dist',
  }
});

This file contains a basic configuration. I's needed to set the input files and the output directory for the build.

Since we intend to compile a Single-page application now, it will be necessary to apply some changes:

import merge from 'deepmerge';
import { createSpaConfig } from '@open-wc/building-rollup';

const baseConfig = createSpaConfig({
  developmentMode: process.env.ROLLUP_WATCH === 'true',
  injectServiceWorker: false
});

export default merge(baseConfig, {
  // any <script type="module"> inside will be bundled by Rollup
  input: './index.html'
});

The baseConfig content will be generated from createSpaConfig, which is defined in @open-wc/building-rollup package.

When createSpaConfig is used, a service worker is generated using Workbox. However, the service worker is injected into the index.html file when injectServiceWorker is enabled.

HTML file as an Input

Once the input parameter is set using an index.html file, any module defined as part of it will be bundled by Rollup. This content will be injected into the HTML file result.

The index.html File

Let's create an index.html file into the root folder with the following content:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>My Single Page Application</title>
</head>
<body>
    <h1>Welcome to your Single Page Application</h1>
    <span>This App uses:</span>
    <ul>
        <li>TypeScript</li>
        <li>Rollup.js</li>
        <li>es-dev-server</li>
    </ul>
    <script type="module" src="./out-tsc/src/app.js"></script>
</body>
</html>

We can say the content of this file is common. However, the most important line would be the reference to the app.js file:

<script type="module" src="./out-tsc/src/app.js"></script>

Let's explain what is happening there:

As you will remember, the tsconfig.json file sets "outDir": "out-tsc" and that means the TypeScript compiler will generate the output files in ./out-tsc folder.
Then, the index.html file does reference to the entry point of the source code, the compiled version of the ./src/app.ts file.
When the Rollup configuration starts to build the app, it will take the module defined in index.html file to generate a bundle ready for it.

Adding Serve and Build Scripts

If you pay attention to the package.json file, it already defines a script to generate the build:

...
"scripts": {
    "build": "rimraf dist && tsc && rollup -c rollup.config.js"
},
...

The change we introduced into the rollup.config.json file doesn't affect the build process.

Now let's move forward with the addition of some scripts to "serve" the application:

... 
"scripts": {
    "tsc:watch": "tsc --watch",
    "start": "concurrently --kill-others --names tsc,web-dev-server \"npm run tsc:watch\" \"web-dev-server --app-index index.html --node-resolve --open --watch\"",
    "build": "rimraf dist && tsc && rollup -c rollup.config.js"
},
...

"tsc:watch" is the script to start with the compilation process through tsc, which is the TypeScript compiler. The --watch param stands for a compiler option to run the compiler in watch mode(it triggers recompilation on file changes).
"start" is the script to add the execution of some commands in parallel: npm run tsc:watch and web-dev-server that includes some CLI flags.
- You already noted that concurrently command is called first!
- The --kill-others parameter will kill all the invoked commands if one dies (either tsc or web-dev-server).

Think for a while how the "start" command is going to look if we're planning to add more configurations in the future: a script that is hard to read and maintain, of course.

Adding the web-dev-server.config.js File

The alternative option to include the CLI flags as parameters is the creation of the web-dev-server.config.js file.

The file extension can be .js, .cjs or .mjs. A .js file will be loaded as an es module or common js module based on your version of node, and the package type of your project.

By default, the Web Dev Server looks at the configuration file in the current working directory.

Let's create the web-dev-server.config.js file in the root folder:

// web-dev-server.config.js

module.exports = {
    port: 8000,
    nodeResolve: true,
    open: true,
    watch: true,
    appIndex: 'index.html',
};

This file now contains the same options we used in the start script with the addition of a custom port number: port: 8000, which can be configured now.

For the sake of simplicity, let's update the start script with a reference to the new configuration file:

... 
"scripts": {
    ...
    "start": "concurrently --kill-others --names tsc,web-dev-server \"npm run tsc:watch\" \"web-dev-server --config web-dev-server.config.js\"",
    ...
},
...

That's it! You're ready to serve your first application using:

npm run start

You should see the following output:

Web Dev Server started...
[web-dev-server] 
[web-dev-server]   Root dir: /Users/luixaviles/projects/typescript-rollup
[web-dev-server]   Local:    http://localhost:8000/
[web-dev-server]   Network:  http://192.168.1.2:8000/
[web-dev-server]

Also, your default browser will be opened to display the index.html content.

On the right side (when you open the Developer Tools), you'll see the output of the main script file. That is proof that the module is running correctly when the SPA is loaded.

Running the Build

The script is ready and doesn't need an update. Execute the following command:

npm run build

This will generate a dist folder with the following content:

|- dist/
    |- 7b857f5b.js
    |- index.html
    |- ... other scripts

A simple way to serve these files locally would be to use the http-server tool (a command-line http server):

http-server dist/ -o

The output of this command will show you the host and the port you need to use to access the build version of the app:

Starting up http-server, serving dist/
Available on:
  http://127.0.0.1:8080
  http://192.168.1.2:8080
Hit CTRL-C to stop the server
open: http://127.0.0.1:8080

I suggest you review the content of dist/ files and make sure you have http-server installed before running the latest command.

Source Code of the Project

Find the complete project in this GitHub repository: typescript-rollup. Do not forget to give it a star ⭐️ and play around with the code.

Feel free to reach out on Twitter if you have any questions. Follow me on GitHub to see more about my work.

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)

Luis Aviles
Luis is a Senior Software Engineer and Google Developer Expert in Web Technologies and Angular. He is an author of online courses, technical articles, and a public speaker. He has participated in different international technology conferences, giving technical talks, workshops, and training sessions. He’s passionate about the developer community and he loves to help junior developers and professionals to improve their skills. When he’s not coding, Luis is doing photography or Astrophotography.
@luixaviles @luixaviles

End-to-end type-safety with JSON Schema

End-to-end type-safety with JSON Schema I recently wrote an introduction to JSON Schema post. If you’re unfamiliar with it, check out the post, but TLDR: It’s a schema specification that can be used to define the input and output data for your JSON API. In my post, I highlight many fantastic benefits you can reap from defining schemas for your JSON API. One of the more interesting things you can achieve with your schemas is end-to-end type safety from your backend API to your client application(s). In this post, we will explore how this can be accomplished slightly deeper. Overview The basic idea of what we want to achieve is: * a JSON API server that validates input and output data using JSON Schema * The JSON Schema definitions that our API uses transformed into TypeScript types With those pieces in place, we can achieve type safety on our API server and the consuming client application. The server side is pretty straightforward if you’re using a server like Fastify with already enabled JSON Schema support. This post will focus on the concepts more than the actual implementation details though. Here’s a simple diagram illustrating the high-level concept: We can share the schema and type declaration between the client and server. In that case, we can make a request to an endpoint where we know its type and schema, and assuming the server validates the data against the schema before sending it back to the client, our client can be confident about the type of the response data. Marrying JSON Schema and TypeScript There are a couple of different ways to accomplish this: * Generating types from schema definitions using code generation tools * Creating TypeBox definitions that can infer TypeScript types and be compiled to JSON Schema I recommend considering both and figuring out which would better fit your application and workflows. Like anything else, each has its own set of trade-offs. In my experience, I’ve found TypeBox to be the most compelling if you want to go deep with this pattern. Code generation A couple of different packages are available for generating TS types from JSON Schema definitions. * https://github.com/bcherny/json-schema-to-typescript * https://github.com/vega/ts-json-schema-generator They are CLI tools that you can provide a glob path to where your schema files are located and will generate TS declaration files to a specified output path. You can set up an npm hook or a similar type of script that will generate types for your development environment. TypeBox TypeBox is a JSON Schema type builder. With this approach, instead of json files, we define schemas in code using the TypeBox API. The TypeBox definitions infer to TypeScript types directly, which eliminates the code generation step described above. Here’s a simple example from the documentation of a JSON Schema definition declared with TypeBox: ` This can then be inferred as a TypeScript type: ` Aside from schemas and types, TypeBox can do a lot more to help us on our type-safety journey. We will explore it a bit more in upcoming sections. Sharing schemas between client and server applications Sharing our JSON Schema between our server and client app is the main requirement for end-to-end type-safety. There are a couple of different ways to accomplish this, but the simplest would be to set up our codebase as a monorepo that contains both the server and client app. Some popular options for TypeScript monorepos are: PNPM, Turborepo, and NX. If a monorepo is not an option, you can publish your schema and types as a package that can be installed in both projects. However, this setup would require a lot more maintenance work. Ultimately, as long as you can import your schemas and types from the client and server app, you are in good shape. Server-to-client validation and type-safety For the sake of simplicity, let's focus on data flowing from the server to the client for now. Generally speaking, the concepts also apply in reverse, as long as your JSON API server validates your inputs and outputs. We’ll look at the most basic version of having strongly typed data on the client from a request to our server. Type-safe client requests In our server application, if we validate the /users endpoint with a shared schema - on the client side, when we make the request to the endpoint, we know that the response data is validated using the user schema. As long as we are confident of this fact, we can use the generated type from that schema as the return type on our client fetch call. Here’s some pseudocode: ` Our server endpoint would look something like this: ` You could get creative and build out a map that defines all of your endpoints, their metadata, and schemas, and use the map to define your server endpoints and create an API client. Transforming data over the wire Everything looks stellar, but we can still take our efforts a bit further. To this point, we are still limited to serialized JSON data. If we have a created_at field (number or ISO string) tied to our user, and we want it to be a Date object when we get a hold of it on the client side - additional work and consideration are required. There are some different strategies out there for deserializing JSON data. The great thing about having shared schemas between our client and server is that we can encode our type information in the schema without sending additional metadata from our server to the client. Using format to declare type data In my initial JSON Schema blog post, I touched on the format field of the specification. In our schema, if the actual type of our date is a string in ISO8601 format, we can declare our format to be "date-time". We can use this information on the client to transform the field into a proper Date object. ` Transforming serialized JSON Data This can be a little bit tricky; again, there are many ways to accomplish it. To demonstrate the concept, we’ll use TypeBox to define our schemas as discussed above. TypeBox provides a Transform type that you can use to declare, encode, and decode methods for your schema definition. ` It even provides helpers to statically generate the decoded and encoded types for your schema ` If you declare your decode and encode functions for your schemas, you can then use the TypeBox API to handle decoding the serialized values returned from your JSON API. Here’s what the concept looks like in practice fetching a user from our API: ` Nice. You could use a validation library like Zod to achieve a similar result but here we aren’t actually doing any validation on our client side. That happened on the server. We just know the types based on the schema since both ends share them. On the client, we are just transforming our serialized JSON into what we want it to be in our client application. Summary There are a lot of pieces in play to accomplish end-to-end type safety. With the help of JSON Schema and TypeBox though, it feels like light work for a semi-roll-your-own type of solution. Another great thing about it is that it’s flexible and based on pretty core concepts like a JSON API paired with a TypeScript-based client application. The number of benefits that you can reap from defining JSON Schemas for your APIs is really great. If you’re like me and wanna keep it simple by avoiding GraphQL or other similar tools, this is a great approach....

Apr 17, 2024

6 mins

JSONTypeScript

How to configure and optimize a new Serverless Framework project with TypeScript

How to configure and optimize a new Serverless Framework project with TypeScript If you’re trying to ship some serverless functions to the cloud quickly, Serverless Framework is a great way to deploy to AWS Lambda quickly. It allows you to deploy APIs, schedule tasks, build workflows, and process cloud events through a code configuration. Serverless Framework supports all the same language runtimes as Lambda, so you can use JavaScript, Ruby, Python, PHP, PowerShell, C#, and Go. When writing JavaScript though, TypeScript has emerged as a popular choice as it is a superset of the language and provides static typing, which many developers have found invaluable. In this post, we will set up a new Serverless Framework project that uses TypeScript and some of the optimizations I recommend for collaborating with teams. These will be my preferences, but I’ll mention other great alternatives that exist as well. Starting a New Project The first thing we’ll want to ensure is that we have the serverless framework installed locally so we can utilize its commands. You can install this using npm: ` From here, we can initialize the project our project by running the serverless command to run the CLI. You should see a prompt like the following: We’ll just use the Node.js - Starter for this demo since we’ll be doing a lot of our customization, but you should check out the other options. At this point, give your project a name. If you use the Serverless Dashboard, select the org you want to use or skip it. For this, we’ll skip this step as we won’t be using the dashboard. We’ll also skip deployment, but you can run this step using your default AWS profile. You’ll now have an initialized project with 4 files: .gitignore index.js - this holds our handler that is configured in the configuration README.md - this has some useful framework commands that you may find useful serverless.yml - this is the main configuration file for defining your serverless infrastructure We’ll cover these in more depth in a minute, but this setup lacks many things. First, I can’t write TypeScript files. I also don’t have a way to run and test things locally. Let’s solve these. Enabling TypeScript and Local Dev Serverless Framework’s most significant feature is its rich plugin library. There are 2 packages I install on any project I’m working on: - serverless-offline - serverless-esbuild Serverless Offline emulates AWS features so you can test your API functions locally. There aren’t any alternatives to this for Serverless Framework, and it doesn’t handle everything AWS can do. For instance, authorizer functions don’t work locally, so offline development may not be on the table for you if this is a must-have feature. There are some other limitations, and I’d consult their issues and READMEs for a thorough understanding, but I’ve found this to be excellent for 99% of projects I’ve done with the framework. Serverless Esbuild allows you to use TypeScript and gives you extremely fast bundler and minifier capabilities. There are a few alternatives for TypeScript, but I don’t like them for a few reasons. First is Serverless Bundle, which will give you a fully configured webpack-based project with other features like linters, loaders, and other features pre-configured. I’ve had to escape their default settings on several occasions and found the plugin not to be as flexible as I wanted. If you need that advanced configuration but want to stay on webpack, Serverless Webpack allows you to take all of what Bundle does and extend it with your customizations. If I’m getting to this level, though, I just want a zero-configuration option which esbuild can be, so I opt for it instead. Its performance is also incredible when it comes to bundle times. If you want just TypeScript, though, many people use serverless-plugin-typescript, but it doesn’t support all TypeScript features out of the box and can be hard to configure. To configure my preferred setup, do the following: 1. Install the plugins by setting up your package.json. I’m using yarn but you can use your preferred package manager. ` Note: I’m also installing serverless here, so I have a local copy that can be used in package.json scripts. I strongly recommend doing this. 2. In our serverless.yml, let’s install the plugins and configure them. When done, our configuration should look like this: ` 3. Now, in our newly created package.json, let’s add a script to run the local dev server. Our package.json should now look like this: ` We can now run yarn dev in our project root and get a running server 🎉 But our handler is still in JavaScript. We’ll want to pull in some types and set our tsconfig.json to fix this. For the types, I use aws-lambda and @types/serverless, which can be installed as dev dependencies. For reference, my tsconfig.json looks like this: ` And I’ve updated our index.js to index.ts and updated it to read as follows: ` With this, we now have TypeScript running and can do local development. Our function doesn’t expose an HTTP route making it harder to test so let’s expose it quickly with some configuration: ` So now we can point our browser to http://localhost:3000/healthcheck and see an output showing our endpoint working! Making the Configuration DX Better ion DX Better Many developers don’t love YAML because of its strict whitespace rules. Serverless Framework supports JavaScript or JSON configurations out of the box, but we want to know if our configuration is valid as we’re writing it. Luckily, we can now use TypeScript to generate a type-safe configuration file! We’ll need to add 2 more packages to make this work to our dev dependencies: ` Now, we can change our serverless.yml to serverless.ts and rewrite it with type safety! ` Note that we can’t use the export keyword for our configuration and need to use module.exports instead. Further Optimization There are a few more settings I like to enable in serverless projects that I want to share with you. AWS Profile In the provider section of our configuration, we can set a profile field. This will relate to the AWS configured profile we want to use for this project. I recommend this path if you’re working on multiple projects to avoid deploying to the wrong AWS target. You can run aws configure –profile to set this up. The profile name specified should match what you put in your Serverless Configuration. Individual Packaging Cold starts#:~:text=Cold%20start%20in%20computing%20refers,cache%20or%20starting%20up%20subsystems.) are a big problem in serverless computing. We need to optimize to make them as small as possible and one of the best ways is to make our lambda functions as small as possible. By default, serverless framework bundles all functions configured into a single executable that gets uploaded to lambda, but you can actually change that setting by specifying you want each function bundled individually. This is a top-level setting in your serverless configuration and will help reduce your function bundle sizes leading to better performance on cold starts. ` Memory & Timeout Lambda charges you based on an intersection of memory usage and function runtime. They have some limits to what you can set these values to but out of the box, the values are 128MB of memory and 3s for timeout. Depending on what you’re doing, you’ll want to adjust these settings. API Gateway has a timeout window of 30s so you won’t be able to exceed that timeout window for HTTP events, but other Lambdas have a 15-minute timeout window on AWS. For memory, you’ll be able to go all the way to 10GB for your functions as needed. I tend to default to 512MB of memory and a 10s timeout window but make sure you base your values on real-world runtime values from your monitoring. Monitoring Speaking of monitoring, by default, your logs will go to Cloudwatch but AWS X-Ray is off by default. You can enable this using the tracing configuration and setting the services you want to trace to true for quick debugging. You can see all these settings in my serverless configuration in the code published to our demo repo: https://github.com/thisdot/blog-demos/tree/main/serverless-setup-demo Other Notes Two other important serverless features I want to share aren’t as common in small apps, but if you’re trying to build larger applications, this is important. First is the useDotenv feature which I talk more about in this blog post. Many people still use the serverless-dotenv-plugin which is no longer needed for newer projects with basic needs. The second is if you’re using multiple cloud services. By default, your lambdas may not have permission to access the other resources it needs. You can read more about this in the official serverless documentation about IAM permissions. Conclusion If you’re interested in a new serverless project, these settings should help you get up and running quickly to make your project a great developer experience for you and those working with you. If you want to avoid doing these steps yourself, check out our starter.dev serverless kit to help you get started....

Jan 26, 2024

7 mins

TypeScriptServerlessAWS

How to Update the Application Title based on Routing Changes in Angular

Have you tried to update the document's title of your application? Maybe you're thinking that applying interpolation should be enough: ` That solution is not going to work since the element is outside of the scope of the Angular application. In fact, the root component of your app is within tag, and the title is part of the element. Luckily, Angular provides the Title service with the methods to read the current title of the application, and a setTitle(title) to update that value. However, what happens if you need to update the title on routing changes? Also, you may consider updating it on certain components for Analytics purposes. In this blog post, I'll explain step-by-step how to create a custom Title service to have full control over the title of the current HTML document for your application. Project Setup Prerequisites You'll need to have installed the following tools in your local environment: - Node.js. Preferably the latest LTS version. - A package manager. You can use either NPM or Yarn. This tutorial will use NPM. Creating the Angular Project Let's assume we'll need to build an application with the following routes as requirements: ` Now, let's create the project from scratch using the Angular CLI tool. ` This command will initialize a base project using some configuration options: - --routing. It will create a routing module. - --prefix corp. It defines a prefix to be applied to the selectors for created components(corp in this case). The default value is app. - --style css. The file extension for the styling files. - --skip-tests. it avoids the generations of the .spec.ts files, which are used for testing Creating the Modules and Components Once we got the initial structure of the app, we'll continue running the following commands to create a separate module for /home and /products, which are the main paths of the project: ` * The --routing flag can be using also along with ng generate module to create a routing configuration file for that module. Creating the Title Service Similar to the previous section, we will create a shared module to hold the Title service. Both can be generated with the following commands: ` * The --module app flag is used to "link" the brand new module to the pre-existing app.module.ts file. The Routing Configuration Open the app-routing.module.ts file, and create the initial routes. ` * By default, the application will redirect to the home path. * When the router loads the home path, a HomeComponent will be rendered. * The products path will be loaded using the _lazy loading_ feature. Pay attention to the data provided to the home path. It contains the configured title through pageTitle string. Next, open the products-routing.module.ts file to enable an additional configuration to load the _Products_ and the _Product Detail_ page. ` * The router will render the ProductsComponent by default when the path matches to /products. This route also defines custom data to be rendered as titles later. * When the path also adds an Id on /products/:id, the router will render the ProductDetailComponent. The Title Service Implementation It's time to implement the custom Title Service for our application. ` The above service implementation could be understood in just a few steps. * First, we'll need to make sure to inject the Router, ActivatedRoute and Title services in the constructor. * The title$ attribute contains the initial value for the title("Corp"), which will be emitted through a _BehaviorSubject_. * The titleRoute$ is an Observable ready to emit any pageTitle value defined in the current route. It may use the parent's _pageTitle_ otherwise. * The titleState$ is an Observable ready to _listen_ to either title$ or titleRoute$ values. In case incoming value is defined, it will call the Angular Title service to perform the update. * The getPageTitle method will be in charge of obtaining the pageTitle of the current route if it is defined or the title of the parent otherwise. Injecting the Title Service One easy way to apply the custom Title Service in the whole application is by updating the app.module.ts file and injecting it into the constructor. ` In that way, once the default component gets rendered, the title will be displayed as Corp - Home. If you click on _Go to Products_ link, then a redirection will be performed and the Title service will be invoked again to display Corp - Products at this time. However, we may need to render a different title according to the product detail. In this case, we'll show Corp - Product Detail - :id where the Id matches with the current route parameter. ` Let's explain the implementation of this component: * The constructor injects the ActivatedRoute and the custom TitleService. * The productId$ is the _Observable_ which is going to emit the Id parameter every time it changes in the URL. * Once the component gets initialized, we'll need to _subscribe_ to the productId$ _Observable_ and then emit a new value for the title after creating a new string using the id. That's possible through the titleService.title$.next() method. * When the component gets _destroyed_, we'll need to _unsubscribe_ from the productIdSubscription. We're ready to go! Every time you select a product, the ProductDetail component will be rendered, and the title will be updated accordingly. Live Demo and Source Code Want to play around with the final application? Just open the following link in your browser: https://luixaviles.github.io/angular-update-title. Find the complete angular project in this GitHub repository: angular-update-title-service. Do not forget to give it a star ⭐️, and play around with the code. Feel free to reach out on Twitter if you have any questions. Follow me on GitHub to see more about my work....

Feb 16, 2022

5 mins

AngularTypeScriptWeb Development

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

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.

How to Serve a Single Page Application (SPA) using Rollup.js and Web Dev Server

What is a SPA (Single-page Application)?

What is Web Dev Server?

Project Setup

Prerequisites

Initialize the Project

Source Code Files

Installing Web Dev Server and Concurrently

TypeScript Configuration

Rollup Configuration

HTML file as an Input

The index.html File

Adding Serve and Build Scripts

Adding the web-dev-server.config.js File

Running the Build

Source Code of the Project

Luis Aviles

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