TypeScript Fundamentals:
A Beginner's Guide

TypeScript, a programming language developed by Microsoft, is a superset of JavaScript. This means that any valid JavaScript code is also valid TypeScript code. However, TypeScript introduces static typing, a feature that allows you to define the data types of variables, functions, and properties. This can lead to more robust, maintainable, and error-free code.

• Improved code quality: Static typing helps you catch errors early in development, preventing bugs from creeping into your application.
• Enhanced code readability: Types provide more context about the expected values of variables and functions, making your code easier to understand.
• Better tooling support: TypeScript offers excellent tooling support, including code completion, type checking, and refactoring, which can significantly improve your development experience.
• Interoperability with JavaScript: TypeScript seamlessly integrates with existing JavaScript code and libraries, making it easy to adapt gradually.

TypeScript introduces a rich type system that allows you to define the expected values of variables, functions, and properties. Here are some of the most common basic types:

Numbers:

• It can represent both integers and floating-point numbers.
• Examples:

  let age: number = 30;
  let pi: number = 3.14159;

Strings:

• Represent sequences of characters.
• Examples:

  let name: string = "Alice";
  let message: string = "Hello, world!";

Booleans:

• Represent true or false values.
• Examples:

  let isLoggedIn: boolean = true;
  let hasError: boolean = false;

Arrays:

• Represent ordered collections of values.
• Examples:

  let numbers: number[] = [1, 2, 3];
  let fruits: string[] = ["apple", "banana", "orange"];

Objects:

• Represent key-value pairs.
• Examples:

  let person: { name: string; age: number; } = {
      name: "Bob",
      age: 25
  };

One of the powerful features of TypeScript is its ability to infer types automatically. This means that in many cases, you don't need to explicitly specify the type of a variable. TypeScript will infer the type based on the value assigned to it.

let x = 10; // TypeScript infers the type of x as number
let y = "Hello"; // TypeScript infers the type of y as string

Note: While type inference is convenient, explicitly specifying types is often good practice, especially for complex data structures or when you want to enforce a particular type.

To get started with TypeScript, you can use a TypeScript compiler or a development environment that supports TypeScript, such as Visual Studio Code. You can also use tools like tsc to compile your TypeScript code into JavaScript.

// app.ts
function greet(name: string): string {
    return "Hello, " + name + "!";
}

let user: string = "John";
let message: string = greet(user);

console.log(message);

To compile this code, you can run the following command in your terminal:

tsc app.ts