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Switching to TypeScript

In this course, learn what TypeScript is, why you should use it instead of vanilla JavaScript, and how to start using it in your own projects.

As the world of JavaScript moves forward, TypeScript continues to become more popular. More companies than ever before are using TypeScript in their codebases, and are heavily preferring it over vanilla JavaScript. But why? What is TypeScript, and why it is so great for developers?

TypeScript logo

What is TypeScript?

If you're familiar with the fundamentals of any programming language (JavaScript included), then you're familiar with the concept of types. String, boolean, array, object, number - these are all types. What TypeScript does is bring type safety to JavaScript, which is normally a dynamically typed and interpreted programming language. This means that if you have declared a variable like this: const foo = 'bar', then later try to access the non-existent property of foo.baz, you'll only know about the error once it happens during runtime.

To sum everything said up above, here's a code example written in JavaScript that has a couple of problems with it:

const john = {
name: 'john',
job: 'web developer',

const bob = {
name: 'bob',
job: 'data analyst',
age: '27',

const addAges = (num1, num2) => num1 + num2;

console.log(addAges(bob.age, john.age));

This code doesn't actually throw an error, but it does output 27undefined. That's not good. The first issue is that john.age is undefined, and the second issue is that bob.age is a string and must be converted to a number to work properly in the addAges function. Despite these two significant mistakes, JavaScript doesn't tell us at all about them and lets the code run with bugs.

With TypeScript, these types of issues stick out like a sore thumb, and depending on your configurations, the compiler will refuse to compile it until they have been fixed.

TS Error 2345

This means that when using TS (a popular acronym for "TypeScript") on a large project, you'll run into much fewer runtime errors and catch the majority of them during the development process.

What are the advantages of using TypeScript?

  1. The ability to optionally statically type your variables and functions.
  2. Type Inference, which provides you the benefits of using types, but without having to actually statically type anything. For example, if you create a variable like this: let num = 5, TypeScript will automatically infer that num is of a number type.
  3. Access to the newest features in JavaScript before they are officially supported everywhere.
  4. Fantastic support with IntelliSense and epic autocomplete when writing functions, accessing object properties, etc. Most IDEs have TypeScript support.
  5. Access to exclusive TypeScript features such as Enums.

How different is TypeScript from JavaScript?

Think of it this way: JavaScript IS TypeScript, but TypeScript isn't JavaScript. All JavaScript code is valid TypeScript code, which means that you can pretty much turn any .js file into a .ts file and it'll still work just the same after being compiled. It also means that to learn TypeScript, you aren't going to have to learn a whole new programming language if you already know JavaScript.

What are the differences? Well, there's really just one: TypeScript files cannot be run directly. They must first be compiled into regular JavaScript.

Ready to get started?

Now that you're familiar with what TypeScript is and aware of its many advantages, let's get started in our TS journey by installing the TypeScript compiler (super easy) and writing our first line of code in a .ts file.