TypeScript vs JavaScript: What are the differences and similarities?

JavaScript has been the go-to language for web development for over two decades, but in recent years, there has been a rise in the popularity of TypeScript. If you are wondering what TypeScript is and how it differs from JavaScript, then you are in the right place!

In this article, we will explore the differences and similarities between TypeScript and JavaScript. We will provide an overview of both languages, and then delve deeper into the specific features that set them apart.

What is JavaScript?

JavaScript is a programming language used primarily for web development. It was created by Brendan Eich in 1995 and has been widely adopted ever since. JavaScript can run on any platform that supports it, including web browsers, servers, and desktop applications. It is an interpreted language, meaning that the code is executed directly by the computer without the need for compilation.

JavaScript is a versatile language that can be used for a variety of tasks, from creating simple animations to building complex web applications. It is the backbone of modern web development and is used by over 70% of developers around the world.

What is TypeScript?

TypeScript is a superset of JavaScript that was created by Microsoft in 2012. It builds on top of the syntax and functionality of JavaScript while adding features that make it easier to write and maintain complex code. TypeScript adds features such as static typing, classes, and interfaces.

TypeScript is often used in large codebases, where maintaining code quality is crucial. It allows developers to catch errors at compile-time rather than run-time, making it easier to avoid bugs and build more reliable software. TypeScript code is transpiled into JavaScript, meaning that it can run on any platform that supports JavaScript.

Without further ado, let's dive into the differences and similarities between TypeScript and JavaScript.

Syntax

The syntax of TypeScript is a superset of JavaScript, meaning that any valid JavaScript code is also valid TypeScript code. TypeScript adds features like classes, interfaces, and enums, but it also contains all of the same statements and expressions as JavaScript.

One of the main differences between TypeScript and JavaScript is that TypeScript allows for static typing. Static typing means that variables, properties, and function parameters can be typed to a specific data type. This allows the TypeScript compiler to catch errors at compile-time instead of run-time.

Here is an example of a static type declaration in TypeScript:

let myString: string = "Hello, World!";

In this example, we are declaring a variable called myString that has a type of string. This means that TypeScript will only allow us to assign string values to this variable.

In JavaScript, variables are dynamically typed, meaning that the data type of a variable can change at runtime. Here is an example of a dynamically typed variable in JavaScript:

let myNumber = 42;
myNumber = "Hello, World!";

In this example, we initialize a variable called myNumber with a value of 42. Later, we assign a string value to the myNumber variable.

Classes

One of the key features of TypeScript is its support for classes. Classes provide a way to create object-oriented code by defining objects that have properties and methods. Classes in TypeScript are similar to those in other object-oriented languages, such as Java and C#.

Here is an example of a class in TypeScript:

class Person {
  private name: string;

  constructor(name: string) {
    this.name = name;
  }

  public sayHello() {
    console.log(`Hello, my name is ${this.name}!`);
  }
}

const person = new Person("John");
person.sayHello(); // Output: "Hello, my name is John!"

In this example, we define a class called Person that has a private property called name, a constructor that takes a name parameter, and a public method called sayHello that logs a greeting to the console. We then create an instance of the Person class and call the sayHello method.

Classes in JavaScript are similar, but they do not have type annotations or visibility modifiers like private or public. Here is an example of a class in JavaScript:

class Person {
  constructor(name) {
    this.name = name;
  }

  sayHello() {
    console.log(`Hello, my name is ${this.name}!`);
  }
}

const person = new Person("John");
person.sayHello(); // Output: "Hello, my name is John!"

Interfaces

Another feature that TypeScript adds to JavaScript is interfaces. Interfaces provide a way to define the shape of an object, including its properties and methods.

Here is an example of an interface in TypeScript:

interface Animal {
  name: string;
  makeSound: () => void;
}

class Dog implements Animal {
  public name: string;

  constructor(name: string) {
    this.name = name;
  }

  public makeSound() {
    console.log("Woof!");
  }
}

const dog = new Dog("Fido");
dog.makeSound(); // Output: "Woof!"

In this example, we define an interface called Animal that requires an object to have a name property and a makeSound() method. We then define a class called Dog that implements the Animal interface. This means that the Dog class must have a name property and a makeSound() method that matches the signature defined in the Animal interface.

Interfaces do not exist in JavaScript, so this feature is unique to TypeScript.

Type Declarations

Another difference between TypeScript and JavaScript is how they handle type declarations. In TypeScript, variables and functions can have explicit type annotations to ensure that the code is correctly typed.

Here is an example of a type declaration in TypeScript:

function sum(a: number, b: number): number {
  return a + b;
}

In this example, we define a function called sum that takes two parameters of type number and returns a value of type number.

JavaScript does not have type annotations, so this code is not valid JavaScript. Instead, JavaScript relies on developers to write code that is correctly typed.

Tooling

One of the main advantages of TypeScript over JavaScript is its tooling support. Because TypeScript provides static typing, it can be analyzed by IDEs and other development tools to provide greater code intelligence and catch errors at compile-time.

For example, code editors like Visual Studio Code provide intellisense for TypeScript code, highlighting errors and providing suggestions for how to fix them.

TypeScript also includes its own compiler that can transform TypeScript code into JavaScript code that can run in any browser or platform that supports JavaScript. This means that TypeScript can be used in any environment where JavaScript is used.

Similarities

Despite their differences, TypeScript and JavaScript share many similarities. They are both based on the ECMAScript specification and are built around the same core features, such as functions, objects, and arrays.

Because TypeScript is a superset of JavaScript, all valid JavaScript code is also valid TypeScript code. This means that developers can start using TypeScript gradually, without having to rewrite their existing JavaScript code.

Conclusion

In conclusion, TypeScript builds on the syntax and functionality of JavaScript by adding features like classes, interfaces, and static typing. These features make it easier to maintain large codebases and catch errors at compile-time.

Despite their differences, TypeScript and JavaScript share many similarities and can be used together in the same codebase.

If you are looking to improve the quality and maintainability of your web applications, TypeScript is definitely worth exploring. Its tooling support and static typing features make it an excellent choice for large codebases and teams of developers.

We hope that this article has provided you with a better understanding of the differences and similarities between TypeScript and JavaScript. Happy coding!

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