TypeScript: What It Is and Why Developers Need It

Introduction

TypeScript is a strongly typed programming language created by Microsoft in 2012. It’s easy to write clean, well-documented, scalable, and maintainable code. TypeScript is used for front-end, back-end, and mobile development, particularly when creating cross-platform mobile apps. It also supports legacy JavaScript projects.

What is TypeScript?

Some developers claim that TypeScript is a superset of JavaScript, since all valid JavaScript code is valid TypeScript. However, it’s more of a dynamic typing add-on. TypeScript was created to make JavaScript code more scalable and secure, eliminate some common errors, and generally simplify work. To achieve this, it added types.

A type is the set of values ​​of a variable, function, or object. For example, if you assign a variable the number type, it will only contain numeric values. Statistical typing is important for defining rules about what operations can and cannot be performed on a variable, function, or object. For example, arithmetic operations can be performed on numeric variables, but not on text variables.

TypeScript vs. JavaScript: Key Advantages

Since TypeScript came after JavaScript, developers had the opportunity to improve those aspects of the language that were causing the most problems and bugs. Here are the main improvements to TypeScript:

1. Static typing. By explicitly specifying types, the developer clearly knows what data format is expected in the code. This minimizes errors at the early stages.
2. Scalability. TypeScript simplifies the maintenance of large projects, where debugging and finding errors without typing can be a problem.
3. Backward and forward compatibility with JavaScript. Since TypeScript is a superset of JavaScript, it easily integrates into existing projects without having to rewrite all the code. This allows you to update old projects without having to completely rewrite them.
4. Modern JavaScript features. TypeScript supports the latest features of the JavaScript language, which allows you to maintain the viability of existing JavaScript projects and create new modern products.
5. Better IDE support. IDEs for TypeScript support autocompletion, compile-time error checking, and code refactoring, which significantly speeds up work.

TypeScript combines the best features of JavaScript with the additional features of TypeScript itself, making this pair a powerful tool for developing modern applications.

How TypeScript Works

TypeScript is a language that requires compilation. TypeScript source code (.ts files) is compiled into JavaScript (.js files), which can then be executed in browsers or on the server. This process allows:

• Check for errors. The TypeScript compiler (tsc) detects and warns about type inconsistencies.
• Optimize code. The resulting JavaScript code after compilation is usually more optimized and understandable.

Example of converting TypeScript to JavaScript:

• TypeScript code.

function add(a: number, b: number): number {
 return a + b;
}
console.log(add(2, 3));

• Compiled JavaScript.

function add(a, b) {
 return a + b;
}
console.log(add(2, 3));

This demonstrates how typing works in TypeScript: a function takes two arguments—a and b—and returns their sum. All types are numeric; attempting to use other types will result in a compile-time error.

Where TypeScript is used

The growing popularity of TypeScript was driven by the demand for JavaScript, as it can be used to solve specific problems, such as scaling existing projects. This opportunity has been recognized by major companies such as Microsoft, Google, and Airbnb. For developers, TypeScript has opened the door to expanding their skill set and improving their qualifications.

Here are examples of using TypeScript for different tasks.

TypeScript and Frontend Development

TypeScript is widely used in user interface development thanks to its integration with popular frameworks.

• Angular. This framework is built entirely on TypeScript. Its strong typing and capabilities simplify the development of complex component-based applications.
• React. Although React natively uses JavaScript, TypeScript is gradually being adopted by most large projects. It helps describe component props (arbitrary input data), preventing errors during development.

TypeScript and Backend Development

TypeScript allows you to create high-performance server-side applications. This is especially useful for working with REST APIs or microservices. The following technologies can be used to create server-side applications with TypeScript:

• NestJS. A server-side application development framework built on TypeScript, it supports a modular architecture and provides built-in tools for working with databases, authorization, and other tasks.
• Express with TypeScript. TypeScript is used to build Express-based servers, taking advantage of strong typing and autocompletion.

Mobile and cross-platform applications

TypeScript is also ideal for developing cross-platform applications that target not only different mobile operating systems but also desktop versions. For this purpose, the following are additionally used:

• Ionic. A platform that enables the creation of hybrid applications using web technologies. TypeScript ensures code stability and predictability.
• NativeScript. A tool for creating native mobile apps using Angular or Vue and TypeScript.

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Enterprise applications

Developers working with large systems are familiar with the challenge of updating them. The internet environment is extremely dynamic and constantly evolving, requiring regular updates. Updating a JavaScript application is often nearly impossible without risking its collapse. Gradually introducing TypeScript into existing projects allows for gradual updates and adaptation to the new environment without rewriting the entire code from scratch.

To do this, we first rename .js files to .ts, add simple type annotations, and then implement more complex TypeScript features, such as interfaces and generics. Interfaces allow us to describe object structures, while generics allow us to create universal functions and classes. This improves application stability and performance, while reducing the time and cost of creating an application from scratch.

Example code in TypeScript with explanation

Here’s some example TypeScript code that demonstrates the language’s core features, including typing, interfaces, classes, and generics.

// Interface for describing the structure of an object
interface Product {
  id: number;
  name: string;
  price: number;
  category?: string; //Optional field
}

// Create an object using an interface
const product: Product = {
  id: 1,
  name: "Laptop",
  price: 1200,
  category: "Electronics",
};

//Function for calculating the total cost of goods
function calculateTotal<T extends { price: number }>(items: T[]): number {
  return items.reduce((total, item) => total + item.price, 0);
}

// Example of an array of products
const products: Product[] = [
  { id: 1, name: "Laptop", price: 1200 },
  { id: 2, name: "Smartphone", price: 800 },
];

// We calculate the total cost
console.log("Total cost:", calculateTotal(products));

// Class with inheritance
class User {
  constructor(public id: number, public name: string) {}

  displayInfo(): void {
    console.log(`ID: ${this.id}, Имя: ${this.name}`);
  }
}

class Admin extends User {
  constructor(id: number, name: string, public role: string) {
    super(id, name);
  }

  displayInfo(): void {
    super.displayInfo();
    console.log(`Роль: ${this.role}`);
  }
}

// Create an instance of the Admin class
const admin = new Admin(1,"Anna", "Administrator");
admin.displayInfo();

This code shows:

• Typing via interfaces. The structure of the Product object is described.
• Generics. The calculateTotal function accepts an array of objects with a price field, which can be anything from Product to something else.
• Classes and inheritance. The Admin class inherits from User, adding its own logic.

Conclusion

TypeScript is a tool that enhances JavaScript, making it more robust and easier to work with. Whether you’re working on small projects or large systems, TypeScript will help you improve code quality, speed up development, and simplify maintenance. If you’d like to improve your developer skills by learning TypeScript, join the TypeScript course, where you’ll master the language from the ground up.

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