As of the end of 2023, JavaScript still stands as the most common programming language used worldwide, with nearly two-thirds (63.61%) of coders using it. However, a relatively new kid on the block – TypeScript –has become very popular in just over a decade since its release. It currently boasts a usage rate of 38.87%, and it’s rapidly catching up to JavaScript in popularity.
That’s not to say that it’s likely to replace JavaScript any time soon. That’s because TypeScript has a few key differences that make it more of a complement to JavaScript rather than a replacement. Here, you’ll discover the key differences between the languages, which may help you decide on which to focus.
What Is JavaScript?
Often referred to as “the programming language for the web,” JavaScript is a scripting language you can use to make your websites and web apps more interactive. It’s typically implemented alongside cascading style sheets (CSS) and hypertext markup language (HTML) by coders who want to introduce a level of dynamism to their sites.
It’s also hugely popular.
According to W3Techs, a staggering 98.4% of websites use JavaScript. Think of it as the language that ties HTML and CSS together, allowing for the implementation of pop-ups, video embedding, drop-down menus, and practically any interactive component of a website.
What Is TypeScript?
TypeScript is a superset of JavaScript, with the key difference being that it includes extra syntax that allows developers to add “types” to their code. In programming, a type is a description of a collection of values the programmer wishes to use in their code. Types also extend to a collection of operations – actions designed to accomplish a task – that require those values to work correctly.
It exists because JavaScript is a little weak when it comes to how loose the language can be. Without offering a way to specify types, it leaves coders with the difficult job of trying to figure out how it passes data around the code. That’s because variable and function parameters don’t contain any information in JavaScript. Instead, developers need to make an educated guess on the data being passed around or, if they’re fortunate, find the information in related documentation.
The most obvious example of JavaScript’s weakness in this area comes when you try to pass a string into a function that’s expecting to receive a number. JavaScript won’t show an error. TypeScript will because it allows you to specify what type of information your function is supposed to receive.
The Key Differences Between JavaScript and TypeScript
With these descriptions, you already see the key difference between the two languages – TypeScript allows you to specify types, and JavaScript doesn’t. For many coders, that’s reason enough to start using TypeScript. They get a language that offers them more structure, as well as one that’s familiar because it’s based on JavaScript.
However, the type issue isn’t the only difference between the two, with the following being some of the most important to know.
Difference 1 – Dynamic vs. Static
JavaScript is a dynamic programming language, whereas TypeScript is a static one.
With a dynamic language, you have a language that’s optimized for speed and is easier to use. That’s because these languages allow you to pass any type of data to a variable, meaning you don’t have to worry about sticking to a specific declaration of the variable’s data type. This distinction allows for more flexibility in your code. You can pass multiple types of data to your variables. However, it also creates the possibility of errors if the data type you pass doesn’t align with the data type required by an operation when you run your code.
A dynamic won’t show those errors until you run the code.
Thus, you’ll end up having to sift through your code to figure out where the bug is rather than being able to locate it instantly.
With a static language, the coder has to declare the date type of every variable they create as part of the process of defining that variable. For instance, if you intend a variable to always contain a number, you have to specify that at the point of creation with a static language. This is much safer for coders. Their script will throw up an error if a variable’s data type isn’t defined. It’s also safer for users of your web application because the code prevents them from entering a data type into a field that won’t be accepted by your system.
For instance, imagine that you have a form that asks for a client’s name and age. Naturally, you’d assume the client will enter a text string for their name and a number for their age. But that may not happen. With a dynamic language, whatever the customer enters into the field gets passed to your system with no error flags. But if you made the form using a static language – such as TypeScript – the form returns an error message so the user can’t enter incompatible data.
The trade-off for TypeScript’s extra safety is that writing code using the language is a little harder. It’ll likely throw up more errors early in the development process, whereas JavaScript will allow you to keep going and handle any errors later.
Difference 2 – Maintenance
Given JavaScript’s dynamic nature, the code created in it tends to be harder to maintain than that created in TypeScript. For example, let’s assume you’re hired to maintain JavaScript code that somebody else has maintained. If they did a sloppy job – especially with their documentation – you may find yourself spending hours determining what their code actually does and what data types it’s supposed to be passing around.
You don’t have that problem with TypeScript.
The code that TypeScript produces is generally easier to read and maintain because the coder has to follow the rules of a static language. In other words, the approach another programmer takes can’t vary from your own too much because they’re working within pre-set restrictions.
Difference 3 – Backward Compatibility
Given that it’s a superset of JavaScript, TypeScript is generally backward compatible with JavaScript. That means you can use code created in JavaScript in TypeScript, up to a point. You’ll still need to declare data types for your variables, per the standards of the static language, but most of the related code ports over with little difficulty.
In short, you can run JavaScript files in TypeScript.
The same can’t be said the other way around because JavaScript can’t run TypeScript files.
Difference 4 – The Amount of Code You Write
Flexibility is the biggest advantage JavaScript offers, and you’ll see that in the amount of code you need to create compared to executing a similar function in TypeScript. Generally, you’ll write less code in JavaScript. Its lack of static constraints allows coders to create shortcuts and get their code to work – albeit with the potential for unforeseen errors – in fewer lines.
TypeScript programs tend to be bulkier because of the language’s static nature. Again, variables and their data type definitions offer the most obvious example. You’ll need a few extra lines to create a variable in TypeScript than you’d need in JavaScript because you have to define the variable’s data type. For a particularly complex program, this could lead to dozens, if not hundreds, of extra lines of code if you need many variables.
In short, JavaScript can be made “leaner” than TypeScript, though you sacrifice some code safety.
Difference 5 – Compiling
This difference is fairly simple – JavaScript doesn’t need to be compiled, whereas TypeScript does.
However, that’s not technically true. While JavaScript doesn’t force you to wait on a compiling process to turn it into machine code, it does use something called “just-in-time” compilation. That method combines the compilation and interpretation processes into one, transforming everything into machine code and executing it all at once.
In practice, it seems that JavaScript executes immediately. But the reality is that the compiling goes on behind the scenes rather than being done in a specific program, as you see with TypeScript. Extra time is added to the process when you have to compile, again emphasizing that JavaScript is usually the faster language in which to code.
Make Your Choice Between JavaScript and TypeScript
Ultimately, your choice between JavaScript and TypeScript comes down to how flexible and fast you want your programming environment to be.
If both of those issues matter to you, JavaScript may be your best choice. As a dynamic language, it places fewer restrictions on you – allowing you to create leaner code – and its “just-in-time” compilation enables you to get to a functioning executable faster. The issue is that this executable may contain errors that JavaScript doesn’t highlight. In-depth documentation is a requirement, both for yourself and any other coders who work on your program.
TypeScript is more rigid, though it’s also familiar to JavaScript coders due to being a superset of the language. Yes, you’ll spend more time creating your programs because you have built-in standards to follow and have to go through the compilation process. However, the time you lose to error-fixing in the early stages of building your program may be made up in the latter stages because your program will generally contain fewer bugs.
It’s a case of flexibility versus safety, with TypeScript excelling for the latter while JavaScript offers more of the former.
