WebAssembly vs JavaScript: Similarities, Differences & Pros And Cons


8 min read

August 29, 2022

Learn how WebAssembly is different from JavaScript and which areas are common for both. This article also compares pros and cons of both languages.

WebAssembly and JavaScript – what’s the relation?

There’re plenty of WebAssembly vs JavaScript conversations going on recently, both online and offline. Which one of those tools will suit you better on your projects? Which gives you more independence, which provides better usability or security? Which one is better for web development and can be interpreted by most of the web browsers?

We have decided to compare them, reflect upon them, and provide you with the best possible answers. To be honest, we already can tell you that there won’t be a winner per se, as neither of them is universally the best choice for every task. We’ll try to highlight the strengths, weaknesses, opportunities, and use cases with both of those languages. Basing on these observations, you should be able to choose whatever suits you best, depending on your priorities.

What is JavaScript?

JavaScript is THE web language of all programmers! JavaScript started as a simple scripting language and was meant to help to introduce some interactivity to web application development. Its main goal was to be easy to learn and write in. Its simplicity and being developer-friendly, as well as its usability, caused its enormous popularity worldwide. But for the same reasons, it wasn’t the fastest solution while programming. Throughout the years, many browsers were adding improvements and optimizations for faster interpretation of JavaScript due to increasing its performance. On the other hand, JavaScript (or JS for short) is one of the high-level languages, often used alongside HTML and CSS. For years it has proven its strategic role, especially since almost all major browsers have JavaScript engines that can execute client-side code.

What is WebAssembly?

WebAssembly is another platform with a huge impact on the entire web application development environment. Thanks to its innovative approach, it was the first time ever that we got solutions previously offered only by high-level languages, JavaScript to be exact. For many years, JS was the only programming language available to use natively in a web browser. Everything has changed with the end of the third-party binary plug-ins that have ruled out other languages, such as Java and Flash’s ActionScript.

It’s important to say that even though WebAssembly brings new language and possibilities to the browser, it’s not at all a JavaScript replacement. The approach we’re facing here is quite unique and innovative and moreover – very different from the Flash plugins and other techniques previously used due to introducing the code into browsers.

Why is it so unique?

WebAssembly (or WASM for short) is a fast, secure and powerful alternative for running code across multiple platforms. It is based on low-level, bytecode, an assembly-like language designed to run natively on web browsers. WebAssembly's initial version was launched in 2017 as an open standard platform supported by W3C, Mozilla, Microsoft, Google, and Apple. It works on the majority of most common browsers, such as Chrome, Edge, Firefox, Safari, and Opera. As of 2022, WebAssembly has become the 4th language of the web (after CSS, JavaScript, and HTML). WebAssembly lets us use source code written in other programming languages, such as C/C++, C#, PHP and Rust to be compiled and run on the web.  

However, unlike JavaScript, WASM isn’t a programming language per se. As its name suggests, it’s rather an assembly language with the ability to compile many other high-level languages into a format that Web browsers can understand.

WebAssembly vs JavaScript: pros and cons

Let's take a quick look at the pros and cons of WebAssembly vs JavaScript to gain a better understanding of what they offer.

The advantages of JavaScript

Many websites, apps and e-commerce stores adopt JavaScript as their main language.  

  • Flexible

The most important reason why JavaScript is so popular is its versatility. Developers can use JavaScript for a wide range of capabilities. It offers great libraries (like React) to build beautiful storefronts, as well solutions like Node.js to power their back-end functionalities.

  • Simple

JavaScript was designed to be easy and simple to learn. Many times it was described as the preferred programming language for beginners. This common opinion made it very popular and this appeal has provided the industry with a highly effective community. As the learning curve for JS is quite low, there is plenty of developers skilled in it, which results in a simpler recruitment process for JS developers in comparison to other languages.

  • Efficient performance

JavaScript is an interpreted language, which means it can perform quite fast, producing optimal speed when used for specific web tasks. This can pump up the developers’ productivity and therefore advocate for the JS’s wide usage and adoption.

  • Libraries and frameworks

Existing libraries and frameworks are very handy and make developer’s lives easier when it comes to programming and developing applications (both web and mobile), as well as other digital products. This is because they can simply choose the functions they need most and benefit from them.

The disadvantages of JavaScript

  • Security

JavaScript is known for its use of scripts (therefore the name). But this characteristic, in particular, adds to the need for the existence of additional processes that unfortunately hackers can abuse. The use and sole existence of unaudited third-party libraries in the JS ecosystem have increased the possibility and in fact the frequency of malicious attacks. This is why, in case you are a system owner, we urge you not to rely solely on client-side validation checks to secure your online applications.

  • Browser Support

Despite the efforts to standardize JavaScript features, developers still have to face some cross-browser compatibility difficulties, sometimes making the creation of the unified UI across all the platforms challenging.

  • Debugging Support failures

Since JavaScript is an interpreted language that does not require a compiler, it’s easy to deploy applications with its use without noticing major difficulties. But at the same time, due to its asynchronous nature, debugging can be complex sometimes and require more effort.

  • DOM interpretation

It’s also worth mentioning that Document Object Model interprets JavaScript slowlier when compared to the code from HTML or WenAssembly.

When to use JavaScript?

JavaScript was primarily designed for adding interactivity to web pages and applications. That said, developers can use JavaScript for several purposes because of its dynamic nature, from embedded systems to desktop and web applications. Examples of the use cases are below.

JavaScript use cases

1. Mobile games

2. Mobile applications development

3. Creating interfaces for Web Applications

4. Powering server-side applications using Node.js.

The advantages of WebAssembly

WebAssembly was designed to conduct high-performance actions. It’s near-native in speed and very satisfying in its quality, despite not being a high-level language.

  • Cross-platform standard

Since WebAssembly code has a cross-platform standard, developers are typically getting great and consistent results from it. This is one of the biggest drivers for WASM's warm reception in the developers’ world since as a result, they can write the code for the web in languages other than JavaScript and port existing applications over the web. Portability is one of the most prominent features of WebAssembly from its beginning, enabling WASM to power efficient applications on various different operating systems.

  • Statically typed

Unlike Javascript, WebAssembly is statically typed, which means code optimization occurs far earlier in the compilation process, before it reaches the browser, leading to better performance and time optimization.

  • Fast

WASM’s binary files are considerably smaller than JavaScript's, resulting in significantly faster loading times. It’s working at a higher speed than other web languages. It also provides the users with faster load times.

  • Portable

One of the main goals of designing WebAssembly was its portability. To run any application on a device, it has to be compatible with the device’s processor architecture and operating system. That means compiling source code for each possible combination of operating systems and processors in the architecture that you want to support. With WebAssembly, you need just one extra step and your app will run in almost every modern browser. The outcome is nearly native code with no installations, local security concerns, or used disk space.

  • Safety

WebAssembly was built with the possible security issues in mind. An occurrence quite common and well known in web development. Therefore WASM's goal was to protect users from potential web insecurities while empowering developers to produce secure applications. WebAssembly’s module system provides a secure application experience by isolating module execution in a sandboxed environment.

The disadvantages of WebAssembly

  • Still in the early stages of development

WebAssembly is still a quite new solution in its early stages of development. Compared to the decades of JavaScript developments, it’ll still take some time before it 's as rich as JS’s ecosystem.  

  • Lack of garbage collection (GC)

One of the cons that developers put focus on is the fact that WebAssembly doesn’t provide a garbage collector. Actually, it involves no tools for memory management. What it does is simply providing you with a block of linear memory. Languages like WebAssembly, that don't use a garbage collection, still need some mechanisms for managing the allocation of memory. Fortunately, with the plans for further development of WebAssembly, there are already talks of adding GC to the new upgrades.

  • DOM support via JS

Instead of interacting with Document Object Model directly, WebAssembly relies on JavaScript.

  • Security

Although WASM was built with security in mind, some features make it useful for malicious attackers. Because WASM is compiled code, browsers might find detecting security issues in the obfuscated format challenging. The same module system that makes the execution in a sandboxed environment possible can bring some potential security issues that could make it easier for criminals to hide malware or execute some phishing attempts.  

  • Language Complexity

One of the biggest drivers of JavaScript adoption is the fact that it’s a high-level language just like Python or Java. This makes it popular among people who want to make an immediate impact. On the contrary, WebAssembly is a low-level language making it more difficult to learn and therefore preventing it from being as popular as JavaScript.

When Should You Use WebAssembly?

Given the benefits of WebAssembly, developers should use it when creating computing-intensive apps. They can use many different languages of their choice and then compile the code to the web using WASM.  

WebAssembly use cases

1. Hybrid-platform apps

2. Developing CPU-intensive games

3. Complicated scientific simulations

4. Music streaming

5. Video rendering

6. Video streaming

7. Image caching

8. Developing sensitive-data applications

The biggest advantage that WASM offers is obviously the fact that it’s working at a higher speed than other web languages. But even with this perk, the developers agree that the WASM code is a great complement, yet not the replacement of JavaScript. They believe that JavaScript will retain its position as the web’s leading dynamic language. WebAssembly can, however, make it possible to add more languages to the Web.

We hope that this portion of knowledge at least has sharpened your appetite for more. In case you want to learn more about JavaScript or WebAssembly, or maybe you just have some other questions that need answering – please do not hesitate to contact us, by clicking the link below.

Created by

Dariusz Żelasko


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