YiXu Zhang

YiXu Zhang


Managing Long-Running Tasks In A React App With Web Workers

In this tutorial, we’re going to learn how to use the Web Worker API to manage time-consuming and UI-blocking tasks in a JavaScript app by building a sample web app that leverages Web Workers.

Response time is a big deal when it comes to web applications. Users demand instantaneous responses, no matter what your app may be doing. Whether it’s only displaying a person’s name or crunching numbers, web app users demand that your app responds to their command every single time. Sometimes that can be hard to achieve given the single-threaded nature of JavaScript. But in this article, we’ll learn how we can leverage the Web Worker API to deliver a better experience.

In writing this article, I made the following assumptions:

  1. To be able to follow along, you should have at least some familiarity with JavaScript and the document API;
  2. You should also have a working knowledge of React so that you can successfully start a new React project using Create React App.

If you need more insights into this topic, I’ve included a number of links in the “Further Resources” section to help you get up to speed.

First, let’s get started with Web Workers.

What Is A Web Worker?

To understand Web Workers and the problem they’re meant to solve, it is necessary to get a grasp of how JavaScript code is executed at runtime. During runtime, JavaScript code is executed sequentially and in a turn-by-turn manner. Once a piece of code ends, then the next one in line starts running, and so on. In technical terms, we say that JavaScript is single-threaded. This behavior implies that once some piece of code starts running, every code that comes after must wait for that code to finish execution. Thus, every line of code “blocks” the execution of everything else that comes after it. It is therefore desirable that every piece of code finish as quickly as possible. If some piece of code takes too long to finish our program would appear to have stopped working. On the browser, this manifests as a frozen, unresponsive page. In some extreme cases, the tab will freeze altogether.

Imagine driving on a single-lane. If any of the drivers ahead of you happen to stop moving for any reason, then, you have a traffic jam. With a program like Java, traffic could continue on other lanes. Thus Java is said to be multi-threaded. Web Workers are an attempt to bring multi-threaded behavior to JavaScript.

The screenshot below shows that the Web Worker API is supported by many browsers, so you should feel confident in using it.

Showing browser support chart for web workers

Web Workers browser support. (Large preview)

Web Workers run in background threads without interfering with the UI, and they communicate with the code that created them by way of event handlers.

An excellent definition of a Web Worker comes from MDN:

“A worker is an object created using a constructor (e.g. Worker()that runs a named JavaScript file — this file contains the code that will run in the worker thread; workers run in another global context that is different from the currentwindow. Thus, using the windowshortcut to get the current global scope (instead ofselfwithin aWorker will return an error.”

A worker is created using the Worker constructor.

const worker = new Worker('worker-file.js')

It is possible to run most code inside a web worker, with some exceptions. For example, you can’t manipulate the DOM from inside a worker. There is no access to the document API.

Workers and the thread that spawns them send messages to each other using the postMessage() method. Similarly, they respond to messages using the onmessage event handler. It’s important to get this difference. Sending messages is achieved using a method; receiving a message back requires an event handler. The message being received is contained in the data attribute of the event. We will see an example of this in the next section. But let me quickly mention that the sort of worker we’ve been discussing is called a “dedicated worker”. This means that the worker is only accessible to the script that called it. It is also possible to have a worker that is accessible from multiple scripts. These are called shared workers and are created using the SharedWorker constructor, as shown below.

const sWorker = new SharedWorker('shared-worker-file.js')

To learn more about Workers, please see this MDN article. The purpose of this article is to get you started with using Web workers. Let’s get to it by computing the nth Fibonacci number.

Computing The Nth Fibonacci Number

Note: For this and the next two sections, I’m using Live Server on VSCode to run the app. You can certainly use something else.

This is the section you’ve been waiting for. We’ll finally write some code to see Web Workers in action. Well, not so fast. We wouldn’t appreciate the job a Web Worker does unless we run into the sort of problems it solves. In this section, we’re going to see an example problem, and in the following section, we’ll see how a web worker helps us do better.

Imagine you were building a web app that allowed users to calculate the nth Fibonacci number. In case you’re new to the term ‘Fibonacci number’, you can read more about it here, but in summary, Fibonacci numbers are a sequence of numbers such that each number is the sum of the two preceding numbers.

Mathematically, it is expressed as:

Thus the first few numbers of the sequence are:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 ...

In some sources, the sequence starts at F<sub>0</sub> = 0, in which case the formula below holds for _n_ > 1:

In this article we’ll start at F1 = 1. One thing we can see right away from the formula is that the numbers follow a recursive pattern. The task at hand now is to write a recursive function to compute the nth Fibonacci number (FN).

After a few tries, I believe you can easily come up with the function below.

const fib = n => {
  if (n < 2) {
    return n // or 1
  } else {
    return fib(n - 1) + fib(n - 2)

The function is simple. If n is less than 2, return n (or 1), otherwise, return the sum of the n-1 and n-2 FNs. With arrow functions and ternary operator, we can come up with a one-liner.

const fib = n => (n < 2 ? n : fib(n-1) + fib(n-2))

This function has a time complexity of 0(2<sup>n</sup>). This simply means that as the value of n increases, the time required to compute the sum increases exponentially. This makes for a really long-running task that could potentially interfere with our UI, for large values of n. Let’s see this in action.

Note: This is by no means the best way to solve this particular problem. My choice of using this method is for the purpose of this article.

To start, create a new folder and name it whatever you like. Now inside that folder create a src/ folder. Also, create an index.html file in the root folder. Inside the src/ folder, create a file named index.js.

Open up index.html and add the following HTML code.

<!DOCTYPE html>
  <link rel="stylesheet" href="styles.css">
  <div class="heading-container">
    <h1>Computing the nth Fibonnaci number</h1>
  <div class="body-container">
    <p id='error' class="error"></p>
    <div class="input-div">
      <input id='number-input' class="number-input" type='number' placeholder="Enter a number" />
      <button id='submit-btn' class="btn-submit">Calculate</button>
    <div id='results-container' class="results"></div>
  <script src="/src/index.js"></script>

This part is very simple. First, we have a heading. Then we have a container with an input and a button. A user would enter a number then click on “Calculate”. We also have a container to hold the result of the calculation. Lastly, we include the src/index.js file in a script tag.

You may delete the stylesheet link. But if you’re short on time, I have defined some CSS which you can use. Just create the styles.css file at the root folder and add the styles below:

body {
    margin: 0;
    padding: 0;
    box-sizing: border-box;

  .heading-container {
    padding: 0 20px;

  .heading-container {
    padding: 20px;
    color: white;
    background: #7a84dd;

  .heading-container > h1 {
    margin: 0;

  .body-container {
    width: 50%

  .input-div {
    margin-top: 15px;
    margin-bottom: 15px;
    display: flex;
    align-items: center;

  .results {
    width: 50vw;

  .results>p {
    font-size: 24px;

  .result-div {
    padding: 5px 10px;
    border-radius: 5px;
    margin: 10px 0;
    background-color: #e09bb7;

  .result-div p {
    margin: 5px;

  span.bold {
    font-weight: bold;

  input {
    font-size: 25px;

  p.error {
    color: red;

  .number-input {
    padding: 7.5px 10px;

  .btn-submit {
    padding: 10px;
    border-radius: 5px;
    border: none;
    background: #07f;
    font-size: 24px;
    color: white;
    cursor: pointer;
    margin: 0 10px;

Now open up src/index.js let’s slowly develop it. Add the code below.

const fib = (n) => (n < 2 ? n : fib(n - 1) + fib(n - 2));

const ordinal_suffix = (num) => {
  // 1st, 2nd, 3rd, 4th, etc.
  const j = num % 10;
  const k = num % 100;
  switch (true) {
    case j === 1 && k !== 11:
      return num + "st";
    case j === 2 && k !== 12:
      return num + "nd";
    case j === 3 && k !== 13:
      return num + "rd";
      return num + "th";
const textCont = (n, fibNum, time) => {
  const nth = ordinal_suffix(n);
  return `
  <p id='timer'>Time:  ${time} ms</p>
  <p> ${nth} fibonnaci number:  ${fibNum}</p>

Here we have three functions. The first one is the function we saw earlier for calculating the nth FN. The second function is just a utility function to attach an appropriate suffix to an integer number. The third function takes some arguments and outputs a markup which we will later insert in the DOM. The first argument is the number whose FN is being computed. The second argument is the computed FN. The last argument is the time it takes to perform the computation.

Still in src/index.js, add the below code just under the previous one.

const errPar = document.getElementById("error");
const btn = document.getElementById("submit-btn");
const input = document.getElementById("number-input");
const resultsContainer = document.getElementById("results-container");

btn.addEventListener("click", (e) => {
  errPar.textContent = '';
  const num = window.Number(input.value);

  if (num < 2) {
    errPar.textContent = "Please enter a number greater than 2";

  const startTime = new Date().getTime();
  const sum = fib(num);
  const time = new Date().getTime() - startTime;

  const resultDiv = document.createElement("div");
  resultDiv.innerHTML = textCont(num, sum, time);
  resultDiv.className = "result-div";

First, we use the document API to get hold of DOM nodes in our HTML file. We get a reference to the paragraph where we’ll display error messages; the input; the calculate button and the container where we’ll show our results.

Next, we attach a “click” event handler to the button. When the button gets clicked, we take whatever is inside the input element and convert it to a number, if we get anything less than 2, we display an error message and return. If we get a number greater than 2, we continue. First, we record the current time. After that, we calculate the FN. When that finishes, we get a time difference that represents how long the computation took. In the remaining part of the code, we create a new div. We then set its inner HTML to be the output of the textCont() function we defined earlier. Finally, we add a class to it (for styling) and append it to the results container. The effect of this is that each computation will appear in a separate div below the previous one.

Showing computed Fibonacci numbers up to 43

Some Fibonacci numbers. (Large preview)

We can see that as the number increases, the computation time also increases (exponentially). For instance, from 30 to 35, we had the computation time jump from 13ms to 130ms. We can still consider those operations to be “fast”. At 40 we see a computation time of over 1 second. On my machine, this is where I start noticing the page become unresponsive. At this point, I can no longer interact with the page while the computation is on-going. I can’t focus on the input or do anything else.

Recall when we talked about JavaScript being single-threaded? Well, that thread has been “blocked” by this long-running computation, so everything else must “wait” for it to finish. It may start at a lower or higher value on your machine, but you’re bound to reach that point. Notice that it took almost 10s to compute that of 44. If there were other things to do on your web app, well, the user has to wait for Fib(44) to finish before they can continue. But if you deployed a web worker to handle that calculation, your users could carry on with something else while that runs.

Let’s now see how web workers help us overcome this problem.

#react #javascript #api #web-development #programming

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Managing Long-Running Tasks In A React App With Web Workers
Autumn  Blick

Autumn Blick


How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

  • Performance: It delivers optimal performance.
  • Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
  • UI design: React Native enables you to design simple and responsive UI for your mobile app.
  • 3rd party plugins: This framework supports 3rd party plugins.
  • Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

  • Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
  • Near-native user experience: React Native provides several native components, and these are platform agnostic.
  • The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

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Fredy  Larson

Fredy Larson


How long does it take to develop/build an app?

With more of us using smartphones, the popularity of mobile applications has exploded. In the digital era, the number of people looking for products and services online is growing rapidly. Smartphone owners look for mobile applications that give them quick access to companies’ products and services. As a result, mobile apps provide customers with a lot of benefits in just one device.

Likewise, companies use mobile apps to increase customer loyalty and improve their services. Mobile Developers are in high demand as companies use apps not only to create brand awareness but also to gather information. For that reason, mobile apps are used as tools to collect valuable data from customers to help companies improve their offer.

There are many types of mobile applications, each with its own advantages. For example, native apps perform better, while web apps don’t need to be customized for the platform or operating system (OS). Likewise, hybrid apps provide users with comfortable user experience. However, you may be wondering how long it takes to develop an app.

To give you an idea of how long the app development process takes, here’s a short guide.

App Idea & Research


_Average time spent: two to five weeks _

This is the initial stage and a crucial step in setting the project in the right direction. In this stage, you brainstorm ideas and select the best one. Apart from that, you’ll need to do some research to see if your idea is viable. Remember that coming up with an idea is easy; the hard part is to make it a reality.

All your ideas may seem viable, but you still have to run some tests to keep it as real as possible. For that reason, when Web Developers are building a web app, they analyze the available ideas to see which one is the best match for the targeted audience.

Targeting the right audience is crucial when you are developing an app. It saves time when shaping the app in the right direction as you have a clear set of objectives. Likewise, analyzing how the app affects the market is essential. During the research process, App Developers must gather information about potential competitors and threats. This helps the app owners develop strategies to tackle difficulties that come up after the launch.

The research process can take several weeks, but it determines how successful your app can be. For that reason, you must take your time to know all the weaknesses and strengths of the competitors, possible app strategies, and targeted audience.

The outcomes of this stage are app prototypes and the minimum feasible product.

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Top Enterprise Angular Web Apps Development Company in USA

AppClues Infotech is one of the leading Enterprise Angular Web Apps Development Company in USA. Our dedicated & highly experienced Angular app developers build top-grade Angular apps for your business with immersive technology & superior functionalities.

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Top 10 React Native App Development Companies in USA

React Native is the most popular dynamic framework that provides the opportunity for Android & iOS users to download and use your product. Finding a good React Native development company is incredibly challenging. Use our list as your go-to resource for React Native app development Companies in USA.

List of Top-Rated React Native Mobile App Development Companies in USA:

  1. AppClues Infotech
  2. WebClues Infotech
  3. AppClues Studio
  4. WebClues Global
  5. Data EximIT
  6. Apptunix
  7. BHW Group
  8. Willow Tree:
  9. MindGrub
  10. Prismetric

A Brief about the company details mentioned below:

1. AppClues Infotech
As a React Native Mobile App Development Company in USA, AppClues Infotech offers user-centered mobile app development for iOS & Android. Since their founding in 2014, their React Native developers create beautiful mobile apps.

They have a robust react native app development team that has high knowledge and excellent strength of developing any type of mobile app. They have successfully delivered 450+ mobile apps as per client requirements and functionalities.
Website: https://www.appcluesinfotech.com/

2. WebClues Infotech
WebClues Infotech is the Top-Notch React Native mobile app development company in USA & offering exceptional service worldwide. Since their founding in 2014, they have completed 950+ web & mobile apps projects on time.

They have the best team of developers who has an excellent knowledge of developing the most secure, robust & Powerful React Native Mobile Apps. From start-ups to enterprise organizations, WebClues Infotech provides top-notch React Native App solutions that meet the needs of their clients.
Website: https://www.webcluesinfotech.com/

3. AppClues Studio
AppClues Studio is one of the top React Native mobile app development company in USA and offers the best service worldwide at an affordable price. They have a robust & comprehensive team of React Native App developers who has high strength & extensive knowledge of developing any type of mobile apps.
Website: https://www.appcluesstudio.com/

4. WebClues Global
WebClues Global is one of the best React Native Mobile App Development Company in USA. They provide low-cost & fast React Native Development Services and their React Native App Developers have a high capability of serving projects on more than one platform.

Since their founding in 2014, they have successfully delivered 721+ mobile app projects accurately. They offer versatile React Native App development technology solutions to their clients at an affordable price.
Website: https://www.webcluesglobal.com/

5. Data EximIT
Hire expert React Native app developer from top React Native app development company in USA. Data EximIT is providing high-quality and innovative React Native application development services and support for your next projects. The company has been in the market for more than 8 years and has already gained the trust of 553+ clients and completed 1250+ projects around the globe.

They have a large pool of React Native App developers who can create scalable, full-fledged, and appealing mobile apps to meet the highest industry standards.
Website: https://www.dataeximit.com/

6. Apptunix
Apptunix is the best React Native App Development Company in the USA. It was established in 2013 and vast experience in developing React Native apps. After developing various successful React Native Mobile Apps, the company believes that this technology helps them incorporate advanced features in mobile apps without influencing the user experience.
Website: https://www.apptunix.com/

7. BHW Group
BHW Group is a Top-Notch React Native Mobile App Development Company in the USA. The company has 13+ years of experience in providing qualitative app development services to clients worldwide. They have a compressive pool of React Native App developers who can create scalable, full-fledged, and creative mobile apps to meet the highest industry standards.
Website: https://thebhwgroup.com/

8. Willow Tree:
Willow Tree is the Top-Notch React Native Mobile App Development Company in the USA & offering exceptional React Native service. They have the best team of developers who has an excellent knowledge of developing the most secure, robust & Powerful React Native Mobile Apps. From start-ups to enterprise organizations, Willow Tree has top-notch React Native App solutions that meet the needs of their clients.
Website: https://willowtreeapps.com/

9. MindGrub
MindGrub is a leading React Native Mobile App Development Company in the USA. Along with React Native, the company also works on other emerging technologies like robotics, augmented & virtual reality. The Company has excellent strength and the best developers team for any type of React Native mobile apps. They offer versatile React Native App development technology solutions to their clients.
Website: https://www.mindgrub.com/

10. Prismetric
Prismetric is the premium React Native Mobile App Development Company in the USA. They provide fast React Native Development Services and their React Native App Developers have a high capability of serving projects on various platforms. They focus on developing customized solutions for specific business requirements. Being a popular name in the React Native development market, Prismetric has accumulated a specialty in offering these services.
Website: https://www.prismetric.com/

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Juned Ghanchi


React Native App Developers India, React Native App Development Company

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We help businesses to scale up the process and achieve greater performance by providing the best react native app development services. Our skilled and experienced team’s apps have delivered all the expected results for our clients across the world.

To achieve growth for your business, hire react native app developers in India. You can count on us for all the technical services and support.

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