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This is why you should go Angular 9 today

I followed almost all of the events around the Angular 9 release. After reading the Angular 9 cheatsheet, reading the Angular next docs, and watching the official release party, I chose to write this article about why you should start using v9 today.

This isn't just a new release, the Angular Team did way more than that. We finally have Ivy, and from now on, it's the recommended option for view rendering. This was a big challenge for them, having so many changes and improvements could make Angular apps feel different, making it harder for developers to adapt. One of the top priorities was making sure the number of breaking changes were the least possible.

Before diving into Ivy and why it is so cool, we are gonna talk about how easy it is to update your Angular to v9.

Update has never been this easy

The Angular Team did their best to reduce the manual changes you have to do. There were new schematics created for ng update to automate the migrations for you.

In some cases, it's as simple as running ng update @angular/core @angular/cli, and you're done. If you want a more in depth, step by step guide, I recommend you to visit the Update Angular Site or you could also check out this Angular Update Guide by Brian Love.

If you came from AngularJS, you know how hard updates have been until now. I personally got stuck in AngularJS until Angular 5, just because I thought there were too many breaking changes. But now, it feels more approachable.

You'll need Typescript version 3.7.

What's up with Ivy?

Ivy is the new view rendering engine. If you are like me, you may be thinking, Wait, what?

I won't dive into it, but we can probably rephrase the claim above, for clarity, by saying Ivy is a new way to manage the templates and projections. I know that isn't much simpler. Luckily, you don't have to care.

Now, you may be scratching your head. As I said, the Angular Team focused on respecting the way Angular works now. They wanted to do this huge change without us noticing it.

The change is under the hood, and we have the same API. This means that there are no changes for you!

What I can tell you is why they did this incredible number of changes

  • Smaller bundle.
  • Better runtime performance.
  • Template type checking.

Having a smaller bundle is one incredibly valuable to users. We get an improved UX by responding quicker, but not only that, we also get an SEO boost by being able to serve users faster. By this, I don't mean that Ivy comes with something specific to boost your SEO, but smaller bundle helps with that. If you want to take your SEO score to the next level, you'll need to explore other options like SSG with Scully or SSR with Angular Universal.

Even though Ivy changes the way templates are rendered, your old DOM selection queries in your e2e tests won't be affected.

The improved runtime performance is just perfect because now it's possible to have AOT enabled even in dev mode. According to members of the Angular Team, this is one of the best things about this new update. I don't know how many times I've forgotten to build the application with AOT enabled before pushing my code, leading to errors down the pipeline that could've been captured.

In order to enhance runtime performance, a lot of things had to change. All querying decorators like ViewChild, ViewChildren, and so on, had several changes to make them more predictable. The team is currently discussing better ways to query, but again, without us noticing it.

Template Type-checking is a game changer. Now, Angular can help you make the templates type safe. This is a major improvement, because now you can have fewer tests, and rely more on the platform. If you want to enforce this in your project, do this in the tsconfig.json file:

{
  // your options,
  "angularCompilerOptions": {
    // your angular compiler options,
    "fullTemplateTypeCheck": true,
    "strictTemplates": true
  }
}

This way, Angular will tell you if you're breaking any typing inside a template at compilation time. But let's see it in action. If you have a component like this:

import { Component, Input } from "@angular/core";

@Component({
  selector: "app-sample",
  templateUrl: "./sample.component.html",
  styleUrls: ["./sample.component.scss"]
})
export class SampleComponent {
  @Input() number: number;
}

And you use it like this:

<app-sample [number]="'text'"></app-sample>

You'll get this error when compiling the application:

TS2322: Type 'string' is not assignable to type 'number'.

Very cool, right?

Working without NgModules is possible, even when compiling a single component, leading to faster unit tests. The Angular Team didn't remove the NgModules to avoid changing the way Angular currently works. They have no plans of stopping their support of NgModules any time soon, but there’s a chance that components and core building blocks will be preferred over modules.

This even makes it possible to access lazy loaded components in a simpler way. If you want to learn more about this, you definitely have to check out Angular 9: Lazy Loading Components by John Papa.

ViewChild now, by default, has { static: false }. Remember that you use static true if you want to access the ElementRef before change detection occurs (ngOnInit).

There’s a new version of TestBed, with the new compiler, that improved the entire pipeline. Time of execution can be reduced up to 40%. In a future release, we’ll be able to use AOT compiled components for unit testing. If you have already updated, feel free to share your statistics.

A few things were removed. Now you can't use Renderer, and you have to start using Renderer2. Thankfully, the ng update schematic takes care of this. The ngForm element selector has been removed, and now can only be called by using ng-form.

Thinking ahead of time

If you are making heavy use of entryComponents, you won't need to do it anymore thanks to Ivy. In v9, its deprecation was announced. Also, we can forget about TestBed.get, and start using TestBed.inject, which has the same behavior, but is type safe.

Ivy unlocks the possibility of making internationalization way better and easier to do, but it isn't there yet. We'll need to keep waiting for a more robust i18n integration into the Angular platform.

We should be moving from ts-lint to es-lint. Sadly, for the case of very large apps, it tends to be slower. Nevertheless, there are people currently working to make it better and faster.

I heard people saying that zone.js was about to die, but that's simply not true. Though it's not included as a part of the browser standard, we still need zone.js for the change detection.

What can you do to help?

  • Update today!
  • Create issues with reproduction
  • If you can help solve an issue, go ahead and join the discussion

References

Conclusion

The Angular Team put a lot of effort into this update, by not only including Ivy, but by also making the ng update schematic even better and easier to use. Now, it's our chance to help them. Let's start using Angular v9 today! Let's all create issues with reproducible repositories that can dramatically help speed up things.

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Drizzle ORM: A performant and type-safe alternative to Prisma

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Understanding Vue's Reactive Data

Introduction Web development has always been about creating dynamic experiences. One of the biggest challenges developers face is managing how data changes over time and reflecting these changes in the UI promptly and accurately. This is where Vue.js, one of the most popular JavaScript frameworks, excels with its powerful reactive data system. In this article, we dig into the heart of Vue's reactivity system. We unravel how it perfectly syncs your application UI with the underlying data state, allowing for a seamless user experience. Whether new to Vue or looking to deepen your understanding, this guide will provide a clear and concise overview of Vue's reactivity, empowering you to build more efficient and responsive Vue 3 applications. So, let’s kick off and embark on this journey to decode Vue's reactive data system. What is Vue's Reactive Data? What does it mean for data to be ”'reactive”? 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Let's say you change this message to 'Goodbye Vue!' later in your code, like when a button is clicked. `javascript state.message = 'Goodbye Vue!'; ` With Vue's reactivity, when you change your data, the UI automatically updates to 'Goodbye Vue!' instead of 'Hello Vue!'. You don't have to write extra code to make this update happen - Vue's Reactive Data system takes care of it. How does it work? Let's keep the mirror example going. Vue's Reactive Data is the mirror that reflects your data changes in the UI. But how does this mirror know when and what to reflect? That's where Vue's underlying mechanism comes into play. Vue has a behind-the-scenes mechanism that helps it stay alerted to any changes in your data. When you create a reactive data object, Vue doesn't just leave it as it is. Instead, it sends this data object through a transformation process and wraps it up in a Proxy. Proxy objects are powerful and can detect when a property is changed, updated, or deleted. Let's use our previous example: `javascript import { createApp, reactive } from 'vue'; const app = createApp({ setup() { const state = reactive({ message: 'Hello Vue!' }); return { state }; } }); app.mount('#app'); ` Consider our “message” data as a book in a library. Vue places this book (our data) within a special book cover (the Proxy). This book cover is unique - it's embedded with a tracking device that notifies Vue every time someone reads the book (accesses the data) or annotates a page (changes the data). In our example, the reactive function creates a Proxy object that wraps around our state object. When you change the 'message': `javascript state.message = 'Goodbye Vue!'; ` The Proxy notices this (like a built-in alarm going off) and alerts Vue that something has changed. Vue then updates the UI to reflect this change. Let’s look deeper into what Vue is doing for us and how it transforms our object into a Proxy object. You don't have to worry about creating or managing the Proxy; Vue handles everything. `javascript const state = reactive({ message: 'Hello Vue!' }); // What vue is doing behind the scenes: function reactive(obj) { return new Proxy(obj, { // target = state and key = message get(target, key) { track(target, key) return target[key] }, set(target, key, value) { target[key] = value // Here Vue will trigger its reactivity system to update the DOM. trigger(target, key) } }) } ` In the example above, we encapsulate our object, in this case, “state”, converting it into a Proxy object. Note that within the second argument of the Proxy, we have two methods: a getter and a setter. The getter method is straightforward: it merely returns the value, which in this instance is “state.message” equating to 'Hello Vue!' Meanwhile, the setter method comes into play when a new value is assigned, as in the case of “state.message = ‘Hey young padawan!’”. Here, “value” becomes our new 'Hey young padawan!', prompting the property to update. This action, in turn, triggers the reactivity system, which subsequently updates the DOM. Venturing Further into the Depths If you have been paying attention to our examples above, you might have noticed that inside the Proxy` method, we call the functions `track` and `trigger` to run our reactivity. Let’s try to understand a bit more about them. You see, Vue 3 reactivity data is more about Proxy objects. Let’s create a new example: `vue import { reactive, watch, computed, effect } from "vue"; const state = reactive({ showSword: false, message: "Hey young padawn!", }); function changeMessage() { state.message = "It's dangerous to go alone! Take this."; } effect(() => { if (state.message === "It's dangerous to go alone! Take this.") { state.showSword = true; } }); {{ state.message }} Click! ` In this example, when you click on the button, the message's value changes. This change triggers the effect function to run, as it's actively listening for any changes in its dependencies__. How does the effect` property know when to be called? Vue 3 has three main functions to run our reactivity: effect`, `track`, and `trigger`. The effect` function is like our supervisor. It steps in and takes action when our data changes – similar to our effect method, we will dive in more later. Next, we have the track` function. It notes down all the important data we need to keep an eye on. In our case, this data would be `state.message`. Lastly, we've got the trigger` function. This one is like our alarm bell. It alerts the `effect` function whenever our important data (the stuff `track` is keeping an eye on) changes. In this way, trigger`, `track`, and `effect` work together to keep our Vue application reacting smoothly to changes in data. Let’s go back to them: `javascript function reactive(obj) { return new Proxy(obj, { get(target, key) { // target = state & key = message track(target, key) // keep an eye for this return target[key] }, set(target, key, value) { target[key] = value trigger(target, key) // trigger the effects! } }) } ` Tracking (Dependency Collection) Tracking is the process of registering dependencies between reactive objects and the effects that depend on them. When a reactive property is read, it's "tracked" as a dependency of the current running effect. When we execute track()`, we essentially store our effects in a Set object. But what exactly is an "effect"? If we revisit our previous example, we see that the effect method must be run whenever any property changes. This action — running the effect method in response to property changes — is what we refer to as an "Effect"! (computed property, watcher, etc.) > Note: We'll outline a basic, high-level overview of what might happen under the hood. Please note that the actual implementation is more complex and optimized, but this should give you an idea of how it works. Let’s see how it works! In our example, we have the following reactive object: `javascript const state = reactive({ showSword: false, message: "Hey young padawn!", }); // which is transformed under the hood to: function reactive(obj) { return new Proxy(obj, { get(target, key) { // target = state | key = message track(target, key) // keep an eye for this return target[key] }, set(target, key, value) { target[key] = value trigger(target, key) // trigger the effects! } }) } ` We need a way to reference the reactive object with its effects. For that, we use a WeakMap. Which type is going to look something like this: `typescript WeakMap>> ` We are using a WeakMap to set our object state as the target (or key). In the Vue code, they call this object `targetMap`. Within this targetMap` object, our value is an object named `depMap` of Map type. Here, the keys represent our properties (in our case, that would be `message` and `showSword`), and the values correspond to their effects – remember, they are stored in a Set that in Vue 3 we refer to as `dep`. Huh… It might seem a bit complex, right? Let's make it more straightforward with a visual example: With the above explained, let’s see what this Track` method kind of looks like and how it uses this `targetMap`. This method essentially is doing something like this: `javascript let activeEffect; // we will see more of this later function track(target, key) { if (activeEffect) { // depsMap` maps targets to their keys and dependent effects let depsMap = targetMap.get(target); // If we don't have a depsMap for this target in our targetMap`, create one. if (!depsMap) { depsMap = new Map(); targetMap.set(target, depsMap); } let dep = depsMap.get(key); if (!dep) { // If we don't have a set of effects for this key in our depsMap`, create one. dep = new Set(); depsMap.set(key, dep); } // Add the current effect as a dependency dep.add(activeEffect); } } ` At this point, you have to be wondering, how does Vue 3 know what activeEffect` should run? Vue 3 keeps track of the currently running effect by using a global variable. When an effect is executed, Vue temporarily stores a reference to it in this global variable, allowing the track` function to access the currently running effect and associate it with the accessed reactive property. This global variable is called inside Vue as `activeEffect`. Vue 3 knows which effect is assigned to this global variable by wrapping the effects functions in a method that invokes the effect whenever a dependency changes. And yes, you guessed, that method is our effect` method. `javascript effect(() => { if (state.message === "It's dangerous to go alone! Take this.") { state.showSword = true; } }); ` This method behind the scenes is doing something similar to this: `javascript function effect(update) { //the function we are passing in const effectMethod = () => { // Assign the effect as our activeEffect` activeEffect = effectMethod // Runs the actual method, also triggering the get` trap inside our proxy update(); // Clean the activeEffect after our Effect has finished activeEffect = null } effectMethod() } ` The handling of activeEffect` within Vue's reactivity system is a dance of careful timing, scoping, and context preservation. Let’s go step by step on how this is working all together. When we run our `Effect` method for the first time, we call the `get` trap of the Proxy. `javascript function effect(update) const effectMethod = () => { // Storing our active effect activeEffect = effectMethod // Running the effect update() ... } ... } effect(() => { // we call the the get` trap when getting our `state.message` if (state.message === "It's dangerous to go alone! Take this.") { state.showSword = true; } }); ` When running the get` trap, we have our `activeEffect` so we can store it as a dependency. `javascript function reactive(obj) { return new Proxy(obj, { // Gets called when our effect runs get(target, key) { track(target, key) // Saves the effect return target[key] }, // ... (other handlers) }) } function track(target, key) { if (activeEffect) { //... rest of the code // Add the current effect as a dependency dep.add(activeEffect); } } ` This coordination ensures that when a reactive property is accessed within an effect, the track function knows which effect is responsible for that access. Trigger Method Our last method makes this Reactive system to be complete. The trigger` method looks up the dependencies for the given target and key and re-runs all dependent effects. `javascript function trigger(target, key) { const depsMap = targetMap.get(target); if (!depsMap) return; // no dependencies, no effects, no need to do anything const dep = depsMap.get(key); if (!dep) return; // no dependencies for this key, no need to do anything // all dependent effects to be re-run dep.forEach(effect => { effect() }); } ` Conclusion Diving into Vue 3's reactivity system has been like unlocking a hidden superpower in my web development toolkit, and honestly, I've had a blast learning about it. From the rudimentary elements of reactive data and instantaneous UI updates to the intricate details involving Proxies, track and trigger functions, and effects, Vue 3's reactivity is an impressively robust framework for building dynamic and responsive applications. In our journey through Vue 3's reactivity, we've uncovered how this framework ensures real-time and precise updates to the UI. We've delved into the use of Proxies to intercept and monitor variable changes and dissected the roles of track and trigger functions, along with the 'effect' method, in facilitating seamless UI updates. Along the way, we've also discovered how Vue ingeniously manages data dependencies through sophisticated data structures like WeakMaps and Sets, offering us a glimpse into its efficient approach to change detection and UI rendering. Whether you're just starting with Vue 3 or an experienced developer looking to level up, understanding this reactivity system is a game-changer. It doesn't just streamline the development process; it enables you to create more interactive, scalable, and maintainable applications. I love Vue 3, and mastering its reactivity system has been enlightening and fun. Thanks for reading, and as always, happy coding!...