If you’re serious about web development, then you’ll need to learn about JavaScript at some point. Year after year, numerous surveys have shown that JavaScript is one of the most popular programming languages in the world, with a large and growing community of developers. Just like Python, modern JavaScript can be used almost anywhere, including the front end, back end, desktop, mobile, and the Internet of Things (IoT). Sometimes it might not be an obvious choice between Python vs JavaScript.
If you’ve never used JavaScript before or have felt overwhelmed by the quick pace of its evolution in recent years, then this article will set you on the right path. You should already know the basics of Python to benefit fully from the comparisons made between the two languages.
In this article, you’ll learn how to:
- Compare Python vs JavaScript
- Choose the right language for the job
- Write a shell script in JavaScript
- Generate dynamic content on a web page
- Take advantage of the JavaScript ecosystem
- Avoid common pitfalls in JavaScript
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JavaScript at a Glance
If you’re already familiar with the origins of JavaScript or just want to see the code in action, then feel free to jump ahead to the next section. Otherwise, prepare for a brief history lesson that will take you through the evolution of JavaScript.
It’s Not Java!
Many people, notably some IT recruiters, believe that JavaScript and Java are the same language. It’s hard to blame them, though, because inventing such a familiar-sounding name was a marketing trick.
JavaScript was originally called Mocha before it was renamed to LiveScript and finally rebranded as JavaScript shortly before its release. At the time, Java was a promising web technology, but it was too difficult for nontechnical webmasters. JavaScript was intended as a somewhat similar but beginner-friendly language to supplement Java applets in web browsers.
Fun Fact: Both Java and JavaScript were released in 1995. Python was already five years old.
To add to the confusion, Microsoft developed its own version of the language, which it called JScript due to a lack of licensing rights, for use with Internet Explorer 3.0. Today, people often refer to JavaScript as JS.
While Java and JavaScript share a few similarities in their C-like syntax as well as in their standard libraries, they’re used for different purposes. Java diverged from the client side into a more general-purpose language. JavaScript, despite its simplicity, was sufficient for validating HTML forms and adding little animations.
It’s ECMAScript
JavaScript was developed in the early days of the Web by a relatively small company known as Netscape. To win the market against Microsoft and mitigate the differences across web browsers, Netscape needed to standardize their language. After being turned down by the international World Wide Web Consortium (W3C), they asked a European standardization body called ECMA (today Ecma International) for help.
ECMA defined a formal specification for the language called ECMAScript because the name JavaScript had been trademarked by Sun Microsystems. JavaScript became one of the implementations of the specification that it originally inspired.
Note: In other words, JavaScript conforms to the ECMAScript specification. Another notable member of the ECMAScript family is ActionScript, which is used on the Flash platform.
While individual implementations of the specification complied with ECMAScript to some extent, they also shipped with additional proprietary APIs. This led to web pages not displaying correctly across different browsers and the advent of libraries such as jQuery.
Are There Other Scripts?
To this day, JavaScript remains the only programming language natively supported by web browsers. It’s the lingua franca of the Web. Some people love it, while others don’t.
There have been—and continue to be—many attempts to replace or supplant JavaScript with other technologies, including:
- Rich Internet Applications: Flash, Silverlight, JavaFX
- Transpilers: Haxe, Google Web Toolkit, pyjs
- JavaScript dialects: CoffeeScript, TypeScript
These attempts were driven not only by personal preference but also by web browsers’ limitations before HTML5 came onto the scene. In those days, you couldn’t use JavaScript for computationally intensive tasks such as drawing vector graphics or processing audio.
Rich Internet Applications (RIA), on the other hand, offered an immersive desktop-like experience in the browser through plugins. They were great for games and processing media. Unfortunately, most of them were closed source. Some had security vulnerabilities or performance issues on certain platforms. To top it off, they all severely limited the ability of web search engines to index pages built with these plugins.
Around the same time came transpilers, which allowed for an automated translation of other languages into JavaScript. This made the entry barrier to front-end development much lower because suddenly back-end engineers could leverage their skills in a new field. However, the downsides were slower development time, limited support for web standards, and cumbersome debugging of the transpiled JavaScript code. To link it back to the original code, you’d need a source map.
Note: While a compiler translates human-readable code written in a high-level programming language straight into machine code, a transpiler translates one high-level language into another. That’s why transpilers are also known as source-to-source compilers. They’re not the same as cross compilers, though, which produce machine code for foreign hardware platforms.
To write Python code for the browser, you can use one of the available transpilers, such as Transcrypt or pyjs. The latter is a port of Google Web Toolkit (GWT), which was a wildly popular Java-to-JavaScript transpiler. Another option is to use a tool like Brython, which runs a streamlined version of the Python interpreter in pure JavaScript. However, the benefits might be offset by poor performance and lack of compatibility.
Transpiling allowed a ton of new languages to emerge with the intent of replacing JavaScript and addressing its shortcomings. Some of these languages were closely related dialects of JavaScript. Perhaps the first was CoffeeScript, which was created about a decade ago. One of the latest was Google’s Dart, which was the fastest-growing language in 2019 according to GitHub. Many more languages followed, but most of them are now obsolete due to the recent advances in JavaScript.
One glaring exception is Microsoft’s TypeScript, which has gained much popularity in recent years. It’s a fully compatible superset of JavaScript that adds optional static type checking. If that sounds familiar to you, that’s because Python’s type hinting was inspired by TypeScript.
While modern JavaScript is mature and actively developed, transpiling is still a common approach to ensure backward compatibility with older browsers. Even if you’re not using TypeScript, which seems to be the language of choice for many new projects, you’re still going to need to transpile your shiny new JavaScript into an older version of the language. Otherwise, you run the risk of getting a runtime error.
Some transpilers also synthesize cutting-edge web APIs, which might be unavailable on certain browsers, with a so-called polyfill.
Today, JavaScript can be thought of as the assembly language of the Web. Many professional front-end engineers tend not to write it by hand anymore. In such a case, it’s generated from scratch through transpiling.
However, even handwritten code often gets processed in some way. For example, minification removes whitespace and renames variables to reduce the amount of data to transfer and to obfuscate the code so that it’s harder to reverse engineer. This is analogous to compiling the source code of a high-level programming language into native machine code.
In addition to this, it’s worthwhile to mention that contemporary browsers support the WebAssembly standard, which is a fairly new technology. It defines a binary format for code that can run with almost-native performance in the browser. It’s fast, portable, secure, and allows for cross compilation of code written in languages like C++ or Rust. With it, for example, you could take the decades-old code of your favorite video game and run it in the browser.
At the moment, WebAssembly helps you optimize the performance of computationally critical parts of your code, but it comes with a price tag. To begin with, you need to know one of the currently supported programming languages. You have to become familiar with low-level concepts such as memory management as there’s no garbage collector yet. The integration with JavaScript code is difficult and costly. Also, there’s no easy way to call web APIs from it.
Note: For a deep dive into WebAssembly, check out The Real Python Podcast - Episode 154 with Brett Cannon.
It seems that, after all these years, JavaScript isn’t going away anytime soon.
JavaScript Starter Kit
One of the first similarities you’ll notice when comparing Python vs JavaScript is that the entry barriers for both are pretty low, making both languages very attractive to beginners who’d like to learn to code. For JavaScript, the only starting requirement is having a web browser. If you’re reading this, then you’ve already got that covered. This accessibility contributes to the language’s popularity.
The Address Bar
To get a taste of what it’s like to write JavaScript code, you can stop reading now and type the following text into the address bar before navigating to it:
The literal text is javascript:alert('hello world'), but don’t just copy and paste it!
That part after the javascript: prefix is a piece of JavaScript code. When confirmed, it should make your browser display a dialog box with the hello world message in it. Each browser renders this dialog slightly differently. For example, Google Chrome displays it like this:
Copying and pasting such a snippet into the address bar will fail in most browsers, which filter out the javascript: prefix as a safety measure against injecting malicious code.
Some browsers, such as Mozilla Firefox, take it one step further by blocking this kind of code execution entirely. In any case, this isn’t the most convenient way of working with JavaScript because you’re constrained to only one line and limited to a certain number of characters. There’s a better way.
Web Developer Tools
If you’re viewing this page on a desktop or a laptop computer, then you can take advantage of the web developer tools, which provide comparable experience across competing web browsers.
Note: The examples that follow use Google Chrome version 80.0. Keyboard shortcuts may vary for other browsers, but the interface should be largely the same.
To toggle these tools, refer to your browser’s documentation or try one of these common keyboard shortcuts:
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F12
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Ctrl+Shift+I
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Cmd