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Ajeet Raina Ajeet Singh Raina is a former Docker Captain, Community Leader and Arm Ambassador. He is a founder of Collabnix blogging site and has authored more than 570+ blogs on Docker, Kubernetes and Cloud-Native Technology. He runs a community Slack of 8900+ members and discord server close to 2200+ members. You can follow him on Twitter(@ajeetsraina).

What is WebAssembly and how it is different from JavaScript

5 min read

So, you’ve probably heard of WebAssembly, right? It’s this cool, low-level binary thing that’s shaking up the web development scene. Instead of being yet another programming language, it’s more like a secret decoder ring for your code.

Think about it this way: you’ve got these high-level languages like C, C++, and Rust, and you want to run them on the web. But the web’s all about JavaScript, and sometimes, JavaScript just can’t handle the heavy lifting. That’s where WebAssembly swoops in. It takes your fancy code and squishes it down into this efficient, compact binary format that browsers can understand lightning-fast. So, your web apps can now handle heavy-duty stuff like graphics rendering and number crunching without breaking a sweat.

What is WebAssembly?

WebAssembly (often abbreviated as Wasm) is an open standard and low-level binary instruction format designed to execute code on the web. It serves as a portable compilation target for high-level languages like C, C++, Rust, and many others, enabling developers to run computationally intensive applications on the web platform with near-native performance.

Wasm is NOT:

  • WebAssembly is not a programming language. It is a binary format that can be used to compile code from other languages, such as C++ and Rust.
  • WebAssembly is not a replacement for JavaScript. JavaScript is still the main language for writing web applications. WebAssembly can be used to speed up certain parts of a web application, but it is not a complete replacement for JavaScript.
  • WebAssembly is not a virtual machine. It is a compiled format that can be executed directly by the browser. This makes it much faster than JavaScript, which is interpreted by the browser.
  • WebAssembly is not a replacement for native code. Native code is code that is written specifically for a particular platform. WebAssembly is not as fast as native code, but it is much faster than JavaScript.
  • WebAssembly is not a silver bullet. It is a powerful tool that can be used to speed up web applications, but it is not a magic bullet. It still requires careful planning and design to be used effectively.

Comparison WebAssembly with other Web Technologies

WebAssembly provides several advantages over other web technologies, including JavaScript and asm.js:

  1. Performance: WebAssembly is designed for high performance, often surpassing the speed of equivalent JavaScript code. It achieves this by utilizing a compact binary format, efficient instruction set, and optimized execution engine.
  2. Language Independence: Unlike JavaScript, which is the de facto language for web development, WebAssembly is language-agnostic. It can be generated from various programming languages, allowing developers to leverage their existing knowledge and choose the language that best fits their needs.
  3. Compatibility: WebAssembly is designed to run alongside JavaScript, seamlessly integrating with existing web projects. It can be easily embedded into HTML documents and interact with JavaScript code, enabling incremental adoption and easy interoperability between the two.
  4. Security: WebAssembly runs in a sandboxed environment, providing a layer of security by preventing direct access to the underlying system. It ensures that untrusted code from the web cannot perform malicious actions or compromise user data.
  5. Size Efficiency: WebAssembly modules are highly compressed and smaller in size compared to equivalent JavaScript code. This results in faster downloads and reduced bandwidth consumption, especially for larger applications or games.

WebAssembly Vs JavaScript

JavaScript has been the cornerstone of web development for decades. It is a high-level, interpreted language that allows developers to create dynamic and interactive web applications. JavaScript runs directly in the browser and provides a wide range of features and APIs for manipulating the Document Object Model (DOM), handling user interactions, making network requests, and much more. It has a massive ecosystem of libraries and frameworks, making it highly versatile for building web applications of varying complexities.

Benefits of JavaScript

While WebAssembly offers improved performance and opens up new possibilities, JavaScript still has several advantages that make it a preferred choice in many web development scenarios:

  • Accessibility: JavaScript is supported by all modern web browsers, ensuring broad compatibility across different platforms and devices. It provides a seamless experience for users without any additional installations or dependencies.
  • Development Speed: JavaScript’s dynamic nature and high-level abstractions make it easy to learn and quick to develop with. Its extensive ecosystem of libraries and frameworks further accelerates the development process.
  • DOM Manipulation: JavaScript has direct access to the browser’s DOM, allowing developers to easily manipulate web page elements, handle events, and create interactive user interfaces.
  • Flexibility: JavaScript’s flexibility allows for rapid prototyping and dynamic adaptation to changing requirements. It supports both functional and object-oriented programming paradigms, making it versatile for a wide range of application scenarios.

Is Wasm better than JavaScript

One of the key advantages of WebAssembly over JavaScript is its performance. JavaScript, being an interpreted language, requires an additional step of parsing and interpreting the code before execution. This can introduce some overhead, especially for computationally intensive tasks. WebAssembly, on the other hand, is designed to be executed by a virtual machine at near-native speed. It achieves this by providing a compact binary format that can be efficiently compiled and executed by modern web browsers. As a result, complex algorithms and applications that require high performance can benefit significantly from WebAssembly.

Let’s take a look at a simple example to compare the performance of WebAssembly and JavaScript. Consider a function to calculate the factorial of a number:

JavaScript implementation

function factorial(n) {
  if (n <= 1) {
    return 1;
  return n * factorial(n - 1);

console.time('JavaScript factorial');
console.timeEnd('JavaScript factorial');

WebAssembly implementation (using C++):

int factorial(int n) {
  if (n <= 1) {
    return 1;
  return n * factorial(n - 1);

The JavaScript implementation calculates the factorial of 10, while measuring the execution time using console.time() and console.timeEnd(). Similarly, the WebAssembly implementation in C++ performs the same calculation. When running these two implementations, you will notice that the WebAssembly version executes significantly faster than the JavaScript version.

Key features and advantages of WebAssembly

WebAssembly boasts several key features and advantages, including:

  1. Efficiency: WebAssembly is designed for efficient execution, allowing complex computations and algorithms to run at near-native speeds. This performance improvement makes it suitable for computationally intensive tasks like gaming, simulations, multimedia processing, and cryptography.
  2. Portability: WebAssembly is supported by multiple platforms, including web browsers, server-side environments like Node.js, and even embedded systems. This portability enables code reuse and deployment across various platforms without significant modifications.
  3. Interoperability: WebAssembly seamlessly integrates with JavaScript and existing web technologies, providing a bridge between different programming languages and the web ecosystem. This interoperability allows developers to leverage existing libraries, frameworks, and APIs while gradually migrating code to WebAssembly.
  4. Offline Execution: WebAssembly modules can be cached and executed offline, providing offline capabilities for web applications. This feature is particularly useful for web-based games, productivity tools, and applications that require consistent performance even in low-connectivity environments.
  5. Ecosystem and Tooling: WebAssembly has a growing ecosystem with a wide range of tools and libraries available. Developers can find compilers, development frameworks, performance optimization tools, and debuggers specifically designed for WebAssembly, making development and deployment more convenient.

WebAssembly’s combination of performance, language independence, compatibility, security, and size efficiency positions it as a powerful tool for modern web development, offering new possibilities and enhanced user experiences.

Will WebAssembly replace JavaScript?

Ah, the age-old question: is WebAssembly the chosen one destined to replace JavaScript as the ruler of the web? Well, let’s dive into that.

Short answer: Nah, not really.

WebAssembly isn’t here to overthrow JavaScript from its throne. Instead, it’s more like a trusty sidekick, swooping in to handle those heavy-duty tasks that JavaScript might struggle with. Think of JavaScript as the friendly neighborhood hero, versatile and reliable, while WebAssembly is the muscle, ready to tackle the tough stuff.

See, JavaScript has been ruling the web kingdom for ages. It’s everywhere, powering everything from simple website interactions to complex web applications. It’s the language of the web, ingrained in our browsers and our hearts (well, maybe not our hearts, but you get the idea).

But sometimes, JavaScript can be a bit… slow. Especially when it comes to crunching numbers or handling super fancy graphics. That’s where WebAssembly steps in. It’s like the secret weapon, optimized for speed and efficiency, allowing us to do things that would make JavaScript break a sweat.

So, rather than replacing JavaScript, WebAssembly complements it. They work together, hand in hand, to create amazing web experiences. You can use JavaScript for all the usual stuff – DOM manipulation, event handling, you name it – and call on WebAssembly when you need that extra oomph.

Plus, WebAssembly plays nice with JavaScript. You can easily integrate it into your existing projects, using it where it makes sense and sticking with JavaScript for everything else. It’s all about teamwork, really.

So, to sum it up: WebAssembly isn’t here to kick JavaScript to the curb. They’re more like the dynamic duo of web development, each bringing their own strengths to the table. And together, they’re unstoppable.

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Ajeet Raina Ajeet Singh Raina is a former Docker Captain, Community Leader and Arm Ambassador. He is a founder of Collabnix blogging site and has authored more than 570+ blogs on Docker, Kubernetes and Cloud-Native Technology. He runs a community Slack of 8900+ members and discord server close to 2200+ members. You can follow him on Twitter(@ajeetsraina).
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