TypeScript vs. JavaScript: Which one to use and why

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This article looks at TypeScript and JavaScript: how they compare and when to use TypeScript and JavaScript. We’ll explore what TypeScript actually is, why it exists, and its pros and cons.

What is TypeScript?

TypeScript is an open source programming language developed and maintained by Microsoft. It’s a superset of JavaScript: all JavaScript code runs in a TypeScript environment.

TypeScript was developed to solve problems that arise when developing large applications in JavaScript. These types of applications contain hundreds of different files. Making a change can affect the behavior of multiple files. Since JavaScript cannot validate the connection between these files, developers have a lot of leeway to make mistakes that cause errors in production. Because of this, a front-end language like TypeScript that includes static type checking was required.

TypeScript is a compiled language as opposed to JavaScript which is an interpreted language. You must compile TypeScript into JavaScript for it to work in a browser. To compile TypeScript into JavaScript you can use the TypeScript npm package.

If you’re coming from an object-oriented language like C# or Java, you’ll find many familiar features in the list that TypeScript adds. My favorites include adding enums, interfaces, access modifiers, namespaces, generics, and more.

Since many external npm libraries are written in JavaScript, TypeScript needed a way to validate them. Here type declaration files (.d.ts files) come into play. These type declarations provide type definitions with information about the code. The compiler uses them to type check TypeScript code. Today most JavaScript libraries have TypeScript definitions written for them. Even if a library lacks these definitions, TypeScript can sometimes infer the types. Alternatively, you can quickly write definitions yourself.

TypeScript is great for rich web applications because you can use it to write frontend and backend code. On the backend, you need to install a library called ts-node to run TypeScript code in a Node.js environment.

What are the advantages of TypeScript over JavaScript?

In 2022, TypeScript was included in the top 5 most used languages ​​worldwide. This isn’t surprising given that TypeScript is always evolving, adding new features, and has a fantastic developer community that the TypeScript team listens to.

TypeScript’s most significant advantage over regular JavaScript is its compiler, which offers type and error checking. It checks type validity and displays errors in real time. It’s especially useful when you’re refactoring your code, as the compiler will show you things you might have missed.

When used in pairs with a newer IDE like Visual Studio Code, TypeScript offers great intellisense features like code hinting and code completion. These features help increase the speed of program development.

Use of tsconfig file, a developer can configure the behavior of TypeScript. For example, TypeScript provides an option to transpile the code to an earlier version of JavaScript, so the code runs on all browsers. Another option a developer has is TypeScript’s strict mode, which adds many more checks to ensure code correctness.

Another great TypeScript feature is the ability to run side-by-side with JavaScript code, making it easier to implement in legacy projects with lots of JavaScript files.

Also, TypeScript allows the use of some ES6 and ES7 candidate features that are not yet supported by major browsers. For example, the optional concatenation operator and class constants were available in TypeScript long before ECMAScript officially supported them.

Finally, TypeScript offers many features that JavaScript lacks, making coding more fun and enjoyable. Features like interfaces, enums, and generics, to name a few, greatly improve the readability of your code.

What are the disadvantages of TypeScript over JavaScript?

Although TypeScript offers several advantages, it also comes with some disadvantages. Neither of these downsides are deal-breakers, but a new developer needs to be aware of them and take them into account.

The most significant disadvantage of TypeScript is the false sense of security it gives its users. When developers come to TypeScript, they often rely too heavily on its compiler, hoping that it will flag any type errors. Don’t expect your TypeScript code to be 100% bulletproof. That’s a decision the TypeScript development team made: TypeScript is meant to be a balance between flexibility and correctness. While TypeScript isn’t bulletproof, I still think it’s better than plain JavaScript code because its compiler catches bugs you wouldn’t otherwise have. In fact, TypeScript is estimated to help find 15% more errors than JavaScript.

Another disadvantage of TypeScript is the additional compilation step required. This step can slow down build time and make the bundler more difficult to set up.

Because TypeScript adds many new features that may be unfamiliar to a front-end developer, it increases a codebase’s learning curve. In fact, when used to its full potential, TypeScript can be difficult to understand for untrained developers and require a lot of Googling or mentoring from older teammates.

TypeScript vs. JavaScript: Complex TypeScript code

Finally, some developers complain that using TypeScript requires adding a lot of extra code to define the types. While this is true, it saves time in the long run because it’s easier to onboard new project members. It also makes codebase refactoring easier.

When should you use TypeScript for a new project?

Adopting a new technology that you are new to can be daunting. With TypeScript, however, it’s worth trying as the pros outweigh the cons.

If you’re working alone on a project and don’t plan on getting any more outside help, I recommend you choose TypeScript for your next web application project. Although setup and the first few hours of development can be difficult, you’ll quickly fall in love with TypeScript and never want to go back to regular JavaScript. You’ll write your code more slowly at first, but TypeScript saves you debugging and refactoring time in the long run.

When working on a project with teammates, the decision is more complex as it requires team and management approval. Although using TypeScript will ultimately help your team, it will slow down development in the short term. Also, the team must be willing to spend some time learning TypeScript, its features, and its best practices. Here, an experienced teammate using TypeScript or another object-oriented programming language (like C#) will help the team make a smooth transition.

If your team is willing to sacrifice short-term performance hits and initial time learning TypeScript, I recommend using TypeScript in your project. You will not regret it.

When should you not use TypeScript for a new project?

While TypeScript is generally awesome, there are still reasons I wouldn’t recommend using it.

The number one reason not to use TypeScript is when you or your team have a tight deadline to meet. Deadlines are stressful enough, and adding new technology that you’re inexperienced with isn’t recommended. Unfortunately, learning TypeScript takes time, and that time could be better spent elsewhere on projects with a deadline.

Also, configuring TypeScript can be tricky, especially for beginners. It may be necessary to install several npm libraries and work with a bundler (like webpack). If you’re not willing to spend the time learning all this new information, don’t use it.

Another thing to consider is that using TypeScript raises the developer’s barrier to entry. If the project is open source, this can increase the difficulty for developers to contribute to it.

Also, for managers and hiring staff, using TypeScript in a project means that the developers you hire must have experience using TypeScript or some other Oops Language. Introducing TypeScript raises the minimum skill set to work on the project and may increase the project’s budget as you need to hire more experienced developers.

TypeScript vs. JavaScript: what about legacy projects?

Migrating a legacy project written with regular JavaScript to TypeScript brings many benefits to the project development lifecycle. It helps to find bugs you didn’t notice and simplifies the maintenance of the project.

For smaller projects, migrating from JavaScript to TypeScript can be done easily by installing the required libraries and changing the file extensions of .js to .tsand fixing the errors thrown by the TypeScript compiler.

Projects with hundreds of different JavaScript files can get more complicated. Luckily, you can gradually adopt TypeScript. You can prioritize migrating some files to TypeScript and running them alongside legacy JavaScript code.

Another option is to keep the old code and only write new functions in TypeScript. If a feature touches some legacy code, you can migrate it at the same time as you work on it.

TypeScript vs JavaScript: the verdict

In this TypeScript vs JavaScript comparison, you saw that TypeScript is a great object-oriented language that lets you build rich applications more efficiently.

Even though it has some downsides like the extra code complexity or the extra compile time, it saves you time in the long run.

If you work alone, I highly recommend building your next application with TypeScript.

If you’re working with a team, adopting TypeScript might take some convincing. I encourage you to start building a TypeScript project in your free time. You can then show it to your teammates and explain all the benefits of TypeScript.

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