Javascript

Understanding Effects In SolidJS

Published Aug 23, 2024

Updated Aug 23, 2024

3 min read

Understanding Effects In SolidJS

In SolidJS, effects are a fundamental concept that helps developers manage side effects and reactive dependencies within their applications. Unlike standard functions that execute once and are done, effects in SolidJS are designed to automatically re-run whenever their dependencies change. This article will explore what effects are, how to use them, manage dependencies, handle multiple signals, and the lifecycle functions that enhance their functionality.

What Are Effects?

Effects in SolidJS are functions that automatically execute when the signals or reactive values they depend on change. This capability makes effects essential for managing side effects like DOM manipulations, data fetching, and subscriptions.

Creating an Effect

To create an effect in SolidJS, you use the createEffect function. This function takes a callback that runs whenever the effect is triggered by a change in its dependencies.

import { createEffect, createSignal } from "solid-js";

const [isOnline, setIsOnline] = createSignal(false);

createEffect(() => {
  console.log(`User is ${isOnline() ? "online" : "offline"}`);
});

// Simulate changing the user's online status
setIsOnline(true); // Output: User is online

In this example, the effect logs the user’s online status to the console. Each time the isOnline signal changes, the effect re-runs and logs the updated status.

Managing Dependencies

Dependencies in effects are the reactive values or signals that an effect observes. When any of these dependencies change, the effect re-runs. Interestingly, SolidJS automatically tracks these dependencies, meaning you don’t need to manually specify them, which reduces the risk of errors.

When an effect is initialized, it runs once even if its dependencies haven't changed. This initial run is useful for setting up the effect, initializing variables, or subscribing to signals.

createEffect(() => {
  console.log("This effect runs once at initialization");
});

createEffect(() => {
  console.log(isOnline()); // This effect runs every time 'isOnline' changes
});

Subscribing to Signals

When an effect observes a signal, it essentially subscribes to it. This subscription allows the effect to re-run whenever the signal's value changes.

import { createSignal, createEffect } from "solid-js";

const [temperature, setTemperature] = createSignal(25);

createEffect(() => {
  console.log(`Current temperature: ${temperature()}°C`);
});

// Update temperature
setTemperature(30); // Output: Current temperature: 30°C

In this example, the effect logs the current temperature whenever it changes.

Managing Multiple Signals

Effects in SolidJS can observe multiple signals simultaneously. This means that a single effect can track changes in multiple reactive values, re-running whenever any of them change.

import { createSignal, createEffect } from "solid-js";

const [temperature, setTemperature] = createSignal(20);
const [humidity, setHumidity] = createSignal(50);

createEffect(() => {
  console.log(`Temperature: ${temperature()}°C, Humidity: ${humidity()}%`);
});

// Update signals
setTemperature(22); // Output: Temperature: 22°C, Humidity: 50%
setHumidity(55);    // Output: Temperature: 22°C, Humidity: 55%

Here, the effect monitors both temperature and humidity signals. It re-runs when either signal changes, ensuring that it always logs the latest values.

Nested Effects

SolidJS allows effects to be nested within each other. Each nested effect independently tracks its own dependencies, ensuring that changes in an inner effect don’t inadvertently trigger an outer effect.

createEffect(() => {
  console.log("Outer effect runs");

  createEffect(() => {
    console.log("Inner effect runs");
  });

  console.log("Outer effect finishes");
});

In this example, changes to dependencies in the inner effect will not affect the outer effect. This separation prevents unintended behaviors and keeps effects isolated from one another.

Lifecycle Functions

SolidJS offers lifecycle functions that give you more control over when effects are initialized and disposed of. This can include running a side effect only once, or cleaning up a task when it is no longer needed.

onMount

The onMount function is used when you need to run a side effect only once, typically when a component is initialized. Unlike effects, which can re-run multiple times, onMount ensures that the callback is executed only once.

import { onMount } from "solid-js";

function WeatherComponent() {
  const [forecast, setForecast] = createSignal(null);

  onMount(async () => {
    const response = await fetch("https://api.weather.com/forecast");
    setForecast(await response.json());
  });

  return <div>Weather Forecast: {forecast() ? forecast().summary : "Loading..."}</div>;
}

This function is perfect for tasks like fetching data or setting up subscriptions that only need to happen once when the component mounts.

onCleanup

The onCleanup function is used to clean up tasks when a component is unmounted. This is particularly useful for clearing intervals, removing event listeners, or unsubscribing from services, thereby preventing memory leaks.

import { onCleanup } from "solid-js";

function TimerComponent() {
  const [time, setTime] = createSignal(0);

  const interval = setInterval(() => {
    setTime((prev) => prev + 1);
  }, 1000);

  onCleanup(() => {
    clearInterval(interval);
  });

  return <div>Elapsed Time: {time()} seconds</div>;
}

In this example, onCleanup ensures that the interval is cleared when the component is unmounted, preventing it from running indefinitely in the background.

Understanding the Execution Model of Effects in SolidJS

SolidJS introduces a fine-grained reactivity system that sets it apart in the UI development landscape. Unlike React, where effects are tied to component lifecycles and can sometimes trigger unnecessary re-renders, SolidJS operates at a much more granular level. It tracks dependencies down to individual signals or computations, enabling highly efficient updates.

When you create an effect using createEffect, SolidJS automatically monitors every reactive signal accessed within that effect. It builds a precise dependency graph, which maps out exactly which effects should be re-executed when specific signals change. This approach ensures that only the necessary parts of your application update in response to state changes, resulting in more efficient rendering and overall better performance.

Conclusion

Effects in SolidJS are a powerful feature that enable you to react to changes in your application's state dynamically. By leveraging createEffect and using lifecycle functions like onMount and onCleanup, you can create robust and responsive applications. Understanding how to effectively use effects will help you build more efficient, maintainable, and bug-free SolidJS applications.

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About the author(s)

Victor Umeh
Software Engineer. Passionate about web developement with specialty in Reactjs and Nextjs. He also interested in web3 and blockchain development. In his free time he plays soccer.
@Vyktoreumeh @vyktoremario

Sharing Signals and Stores: Context API in SolidJS

Introduction Welcome to our latest blog post on SolidJS, where we delve into the world of the Context API. Context API is a popular and versatile feature in SolidJS, allowing developers to pass data and functions through the component tree without the need for props drilling. In this post, we will discuss how SolidJS implements the Context API, including the creation of contexts, sharing Signals and stores, and utilizing them within the components. Whether you are a seasoned developer, or just starting out, this post will provide valuable insights into the use of Context API in SolidJS and what are the advantages in the Reactivity ecosystem. So sit back, grab a cup of coffee, and let's dive in! What is SolidJS? SolidJS is a unique and powerful JavaScript framework that is quickly gaining popularity among developers. One of the key features that sets SolidJS apart from other frameworks is its reactive nature. How about reactivity? Reactivity is a programming paradigm through which the application automatically updates and re-renders when the data changes. This means that developers do not have to manually update the view when the data changes, saving a lot of time and effort. SolidJS achieves this reactivity by using a virtual DOM which is a lightweight representation of the actual DOM. This virtual DOM is then used to update the actual DOM, making the process of updating the view much faster and more efficient. Performance Another advantage of SolidJS is its performance. SolidJS is designed to be fast and efficient thanks to its use of a virtual DOM and a functional programming approach. By using functional components and immutability, SolidJS is able to optimize the process of re-rendering, resulting in a smoother and more responsive user experience. In addition to its reactivity and performance, SolidJS also has a small footprint and a simple API. The framework is lightweight and easy to learn, making it a great choice for developers of all skill levels. Signals: SolidJS Signals are a powerful feature that allow for easy communication between different parts of your application. They are similar to events or hooks in other frameworks, but with a few key differences. One of the key advantages of Signals in SolidJS is that they are fully reactive, meaning that they automatically update and re-render when the data changes. This makes it easy to create responsive and dynamic applications without having to manually update the view. To use Signals in SolidJS, you need to first create a signal by using the createSignal function. ` Store In SolidJS, a store works similar to other frontend frameworks. To keep things light, SolidJS creates underlying Signals only for properties that are accessed under tracking scopes. All Signals in Stores are created lazily as requested. The createStore call takes the initial value, and returns a read/write tuple similar to Signals. The first element is the store proxy which is readonly, and the second is a setter function. What About context? SolidJS provides a context API to pass data around without relying on passing props; this is useful in sharing Signals and Stores as described above. According to SolidJS docs: “Using Context has the benefit of being created as part of the reactive system and managed by it.” Getting Started: First, let’s create our context: ` Then we can consume our recently Context created: ` To use context, we'll first wrap our App component in order to provide it globally: ` We can now consume the context and our components will look like this: ` ` Conclusion In this article, we were able to use the contextAPI to share the props we want across the app, and benefit from the performance of Reactivity because of that. This will make our application more readable, but also brings some additional benefits to the app which are as follows: - avoid passing props down through multiple levels of the component tree. - reducing the number of re-renders that occur when props are passed down. - by isolating state and props to a specific context, you can make your code more organized and easier to understand. - components that use the Context API are more easily tested. Would you like to learn more about Signals and Stores, or SolidJS in general? You can see in detail how this was maximized in one of This Dot Labs' open source project starter.dev GitHub Showcases....

Mar 10, 2023

3 mins

SolidJS

Deep Dive Into How Signals Work In SolidJS

SolidJS and Qwik have shown the world the power of signals, and Angular is following suit. There’s no way around them, so let's see what they are, why one would use them, and how they work. Signal basics Signals are built using the observer pattern. In this pattern, a subject holds a list of observers who are subscribed to changes to the subject. Whenever the subject gets changed, all subscribers will receive a notification of the update. Typically through a registered callback method. Observers may push new changes to that subject or other subjects. Triggering another set of updates throughout the observers. > From the above, you might have guessed that infinite loops are a big caveat with using the observer pattern. The same holds true for signals. The power of this pattern lies in the separation of concerns. Observers need to know little about the subject, except that it can change. Whichever actor is going to change the subject needs to know nothing about the observers. This makes it easy to build standalone services that know only about their domain. Signals in front-end frameworks SolidJS brings the observer pattern to the table for front-end frameworks through signals. Observers can be added to a signal through SolidJS’s concept of Effects (by using createEffect). Components within SolidJS can be seen as both an observer and a subject at the same time. The component subscribes to all signals that are used to render the components HTML. SolidJS’s rendering system, in turn, is subscribed to all components. Where the components act as subjects and SolidJS as an observer. So whenever a signal changes in a component, the component reacts by changing its output, which then triggers SolidJS to put the new output on the screen. Compare this to, for example, Vue or React. When a change to the state occurs, the new values are passed down the component hierarchy. Each component returns its new output, which can be either the same as the previous render or changed. The framework then compares this tree against what it already had, and determines which parts to update. This is more dependent on a single source of truth which needs to know about all the components in the system. Changes are loosely related to each other, and only by diffing the results can the next step be determined. This differs from SolidJS setup, which makes hard connections between changes and results, making what will get updated when a signal changes more straightforward. Writing our own Signals At first sight, signals seem magical, and one might be inclined to believe there are some compiler tricks going on. Yet it is all plain JavaScript, and in this article, we’ll demystify signals in order to use them to their full potential. We can create our own signals with pure JavaScript in less than 25 lines. > Our simple version will not take objects or arrays as values as these are references in JavaScript and require special attention. Let's start with the interface. We want the signal creator, which is a function that returns a tuple with the first value being the getter and the second value the setter. The function accepts a value, which will be used as the initial value. This gives us: ` > Note that, due to the fact that we created a new variable within the closure of our createSignal, the variable outside of its scope will not change. original on the last line will still be “1”. For simplicity, we’re going to leave objects and arrays out of the picture as these are references instead of scalar values, and need extra code to do the same thing. Now that we can read from and write to our signal (a.k.a. subject), we’ll need to add subscribers to it. Whenever the getter is called (i.e., the value is read), we want the originator of the call to be registered as an observer. Then, when the setter is called, we are going to loop over all subscribed observers, and notify them of the new value. Consider this fully working signal creator. We’re almost there. ` This snippet has a downside. It needs the observer to be passed as the argument to the getter. But we don’t want to deal with that. Our interface was to read signal(), and have some sort of magic register the observer for us. What comes next was an eye-opener for me. I always believed there was some closure trick, or built-in JavaScript function to retrieve parent closures. That would have been a fantastic way to get who called the getter function and register it as an observer. But JavaScript offers nothing to support us in this. Instead, a way more simple trick is used, and it is seemingly used in every major framework. Frameworks, among others, React and SolidJS, store the parent in a global variable. Because JavaScript is single-threaded, it needs to execute all operations in order. It does a lot under the hood to get stuff like async to work. Clever developers have relied on this single-threaded aspect by writing to a global variable, and reading from it in the next function. This gets a little abstract, so here’s a concrete example to demonstrate this setup. ` We do not need to worry about current getting overwritten, as the code will always execute in order. It’s safe to assume that it will have the value we expect it to have when the body of second is executed. Note that we clear the value in the body of first as we don’t want unwanted side-effects by leaving the variable set. The Fully Working Signal Let’s add effects to our signals to complete the minimal signal minimal framework. With what we have learned in the previous section, we can create effects by Registering the effect callback (i.e., the observer) to our global variable current Calling the observer for the first time. This will read all signals it depends upon, therefore adding current to the observer list. Clearing current to prevent registering the observer to signals read in the future. For this, we remove the current argument from the getter, as this is now globally readable. And we can add the createEffect function. ` With this setup, we already have a working signal system. We can register effects and write out signals to trigger them. ` And there we have it! Working signals in just a couple of lines, no magic, no difficult JavaScript API. All just plain code. You can play around with the fully working example in this StackBlitz project. It has the signal setup as described, plus an example of stores. Run node index.js to see the result. This simple framework is only focused on showcasing signals. For demonstration purposes, it simply logs to the console. Frameworks like SolidJS have advanced effects and logic to get HTML rendering to work. If you’re interested in learning more about rendering, you can read Mark’s blog on how to create your own custom renderer in SolidJS Or put your newly learned skills to use in a new SolidJS project created with Starter.dev’s SolidJS and Tailwind starter!...

May 8, 2023

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How to test React custom hooks and components with Vitest

Introduction In this guide, we'll navigate through the process of testing React hooks and components using Vitest—a powerful JavaScript unit testing framework. Discover how Vitest simplifies testing setups, providing an optimal solution for both Vite-powered projects and beyond. Vitest is a javascript unit testing framework that aims to position itself as the Test Runner of choice for Vite projects and as a solid alternative even for projects not using Vite. Vitest was built primarily for Vite-powered projects, to help reduce the complexity of setting up testing with other testing frameworks like Jest. Vitest uses the same configuration of your App (through vite.config.js), sharing a common transformation pipeline during dev, build, and test time. Prerequisites This article assumes a solid understanding of React and frontend unit testing. Familiarity with tools like React Testing Library and JSDOM will enhance your grasp of the testing process with Vitest. Installation and configuration Let’s see how we can use Vitest for testing React custom hooks and components. But first, we will need to create a new project with Vite! If you already have an existing project, you can skip this step. ` Follow the prompts to create a new React project successfully. For testing, we need the following dependencies installed: Vitest as the unit testing framework JSDOM as the DOM environment for running our tests React Testing Library as the React testing utilities. To do so, we run the following command: ` Once we have those packages installed, we need to configure the vite.config.js file to run tests. By default, some of the extra configs we need to set up Vitest are not available in the Vite config types, so we will need the vite.config.ts file to reference Vitest types by adding /// reference types=”vitest” /> at the top of the file. Add the following code to the vite.config.ts ` We set globals to true because, by default, Vitest does not provide global APIs for explicitness. So with this set to true, we can use keywords like describe, test and it without needing to import them. To get TypeScript working with the global APIs, add vitest/globals to the types field in your tsconfig.json. ` The environment property tells Vitest which environment to run the test. We are using jsdom as the environment. The root property tells Vitest the root folder from where it should start looking for test files. We should add a script for running the test in package.json ` With all that configured, we can now start writing unit tests for customs hooks and React components. Writing test for custom hooks Let’s write a test for a simple useCounter hook that takes an initial value and returns the value, an increment function and a decrement function. ` We can write a test to check the default return values of the hook for value as below: ` To test if the hook works when we increment the value, we can use the act() method from @testing-library/react to simulate the increment function, as shown in the below test case: ` Kindly Note that you can't destructure the reactive properties of the result.current instance, or they will lose their reactivity. Testing hooks with asynchronous logic Now let’s test a more complex logic that contains asynchronous logic. Let’s write a useProducts hook that fetches data from an external api and return that value ` Now, let’s see what the test looks like: ` In the above example, we had to spy on the global fetch API, so that we can mock its return value. We wrapped that inside a beforeAll so that this runs before any test in this file. Then we added an afterAll method and called the mockRestore() to run after all test cases have been completed and return all mock implementations to their original function. We can also use the mockClear() method to clear all the mock's information, such as the number of calls and the mock's results. This method is handy when mocking the same function with different return values for different tests. We usually use mockClear() in beforeEach() or afterEach() methods to ensure our test is isolated completely. Then in our test case, we used a waitFor(), to wait for the return value to be resolved. Writing test for components Like Jest, Vitest provides assertion methods (matchers) to use with the expect methods for asserting values, but to test DOM elements easily, we will need to make use of custom matchers such as toBeInTheDocument() or toHaveTextContent(). Luckily the Vitest API is mostly compatible with the Jest API, making it possible to reuse many tools originally built for Jest. For such methods, we can install the @testing-library/jest-dom package and extend the expect method from Vitest to include the assertion methods in matchers from this package. ` After installing the jest-dom testing library package, create a file named vitest-setup.ts on the root of the project and import the following into the project to extend js-dom custom matchers: ` Since we are using typescript, we also need to include our setup file in our tsconfig.json: ` In vite.config.ts, we need to add the vitest-setup.ts file to the test.setupFiles field: ` Now let’s test the Products.tsx component: ` We start by spying and mocking the useProducts hook with vi.spyOn() method from Vitest: ` Now, we render the Products component using the render method from @testing-library/react and assert that the component renders the list of products as expected and also the product has the title as follows: ` In the above code, we use the render method from @testing-library/react to render the component and this returns some useful methods we can use to extract information from the component like getByTestId and getByText. The getByTestId method will retrieve the element whose data-testid attribute value equals product-list, and we can then assert its children to equal the length of our mocked items array. Using data-testid attribute values is a good practice for identifying a DOM element for testing purposes and avoiding affecting the component's implementation in production and tests. We also used the getByText method to find a text in the rendered component. We were able to call the toBeInTheDocument() because we extended the matchers to work with Vitest earlier. Here is what the full test looks like: ` Conclusion In this article, we delved into the world of testing React hooks and components using Vitest, a versatile JavaScript unit testing framework. We walked through the installation and configuration process, ensuring compatibility with React, JSDOM, and React Testing Library. The comprehensive guide covered writing tests for custom hooks, including handling asynchronous logic, and testing React components, leveraging custom matchers for DOM assertions. By adopting Vitest, developers can streamline the testing process for their React applications, whether powered by Vite or not. The framework's seamless integration with Vite projects simplifies the setup, reducing the complexities associated with other testing tools like Jest....

Mar 15, 2024

5 mins

ViteReactTesting

How Nuxt Studio is Redefining Developer & User Experience with Baptiste Leproux & Ferdinand Coumau

In this episode of the Modern Web Podcast, Danny Thompson sits down with Ferdinand Como and Baptiste Leproux from Nuxt Labs to uncover the story behind Nuxt Studio, a tool that's transforming how developers and non-technical users interact with Nuxt applications. Ferdinand and Baptiste share how Nuxt Studio bridges the gap between developer customization and user-friendly content management. Built to empower agencies, freelancers, and their clients, Nuxt Studio combines powerful features like live previews, Vue component integration, and schema-driven forms to make managing content seamless. The conversation also explores the broader mission of Nuxt Labs—building sustainable open-source tools that enhance developer experience and meet real-world needs. With insights into the future of Nuxt Studio and its potential to scale for larger organizations, this episode is a must-listen for anyone passionate about innovation in web development. Chapters 1. Introduction and Setting the Stage (00:00:00) 2. The Vision Behind Nuxt Studio (00:03:10) 3. Nuxt Studio’s Core Features (00:08:45) 4. Challenges in Building Nuxt Studio (00:16:20) 5. Target Audience and Use Cases (00:22:35) 6. Sustainability in Open Source (00:29:00) 7. The Future of Nuxt Studio (00:35:10) 8. Nuxt Studio’s Role in the Nuxt Ecosystem (00:42:30) 9. Closing Thoughts and What’s Next (00:48:00) 10. Sponsor Shoutout and Wrap-Up (00:53:20) Follow Baptiste Leproux and Ferdinand Coumau Baptiste Twitter: https://x.com/_larbish Ferdinand Twitter: https://x.com/CoumauFerdinand Baptiste Linkedin: https://www.linkedin.com/in/baptiste-leproux-618842b0/ Ferdinand Linkedin: https://www.linkedin.com/in/ferdinand-coumau-nuxt/ Sponsored by This Dot: thisdot.co...

Nov 20, 2024

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Understanding Effects In SolidJS

Understanding Effects In SolidJS

What Are Effects?

Creating an Effect

Managing Dependencies

Subscribing to Signals

Managing Multiple Signals

Nested Effects

Lifecycle Functions

onMount

onCleanup

Understanding the Execution Model of Effects in SolidJS

Conclusion

Victor Umeh

You might also like

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Let's innovate together!

You might also like

Sharing Signals and Stores: Context API in SolidJS

Deep Dive Into How Signals Work In SolidJS

How to test React custom hooks and components with Vitest

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