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TypeScript fundamentals, static typing, interfaces, generics, advanced types, tooling, and large-scale application development.
May 30, 2026
Learn TypeScript fundamentals, static typing, interfaces, functions, and why TypeScript has become the standard for modern JavaScript development.
June 10, 2026
TypeScript Fundamentals: Why JavaScript Developers Need Types Introduction JavaScript is one of the most successful programming languages ever created. It powers websites, backend servers, desktop applications, mobile applications, and even cloud infrastructure. However, JavaScript was originally designed as a scripting language for browsers. As applications became larger and more complex, developers began encountering problems that JavaScript could not detect before the code was executed. To solve these problems, Microsoft created TypeScript. TypeScript Is a Superset of JavaScript TypeScript builds on top of JavaScript. Every valid JavaScript program is also valid TypeScript. TypeScript does not replace JavaScript. Instead, it extends JavaScript by adding a static type system and better tooling. Some Strange JavaScript Behaviors These behaviors are legal JavaScript, but they can become problematic in large applications. TypeScript Adds Types A type describes what kind of value a variable can store. Static Type Checking TypeScript performs static type checking before code executes. This allows many errors to be detected during development rather than at runtime. Browsers Cannot Execute TypeScript Browsers understand JavaScript, not TypeScript. TypeScript must be transpiled into JavaScript before execution. Installing TypeScript This provides the TypeScript compiler: Compiling TypeScript The compiler generates an app.js file. TypeScript Playground The TypeScript Playground provides an online environment where you can experiment with TypeScript and inspect the generated JavaScript. Summary TypeScript is JavaScript with an additional type system. It helps developers catch mistakes before runtime and makes large applications easier to maintain.
June 10, 2026
TypeScript Types, Inference and Functions Primitive Types TypeScript provides several built-in primitive types. Type Inference TypeScript often figures out types automatically. This process is called type inference. Better Editor Support Because TypeScript knows the type of a variable, editors can provide autocomplete and intelligent suggestions. Compilation Still Happens With Errors TypeScript reports an error, but JavaScript can still be generated depending on compiler settings. The Any Type The any type disables type checking. Implicit Any When TypeScript cannot determine a type, it may infer any. Function Parameters Return Types Default Parameters Void Contextual Typing TypeScript infers that color is a string. Never A function returning never never successfully completes. Summary Type inference, function typing, any, void, and never form the foundation of everyday TypeScript development.
June 10, 2026
TypeScript Objects, Arrays, Unions and Tuples Object Types Excess Property Checks TypeScript reports an error for excess properties when passed inline. Type Aliases Nested Types Optional Properties Readonly Properties Intersection Types Array Types Union Types Type Narrowing Union Arrays Literal Types Tuples React and Tuples Tuples are commonly used in React hooks. Tuples vs Objects Objects are often easier to understand because property names provide context, while tuples rely on position. Enums JavaScript does not have built-in enums. TypeScript adds enums as a way to group related named constants together. Key Points Enum names and members are commonly capitalized. Numeric enums start at 0 by default. Subsequent values are automatically incremented. You can also assign values explicitly. Enums and Databases String Enums Mixed Enums Enums vs Objects Interfaces Interfaces are another way to describe the shape of an object in TypeScript. In many cases, interfaces and type aliases can be used interchangeably, but there are some important differences. Basic Interface This is very similar to a type alias: Optional and Readonly Properties Interfaces support optional properties using ? and readonly properties using the readonly keyword. Function Properties Interfaces can describe functions that belong to an object. Type aliases can also define function properties. Extending Interfaces The Employee interface automatically includes all properties from Person. Extending Type Aliases Type aliases cannot use extends, but similar behavior can be achieved using intersection types (&). Interfaces vs Union Types Interfaces cannot directly represent union types. For this reason, type aliases are often preferred when working with unions and literal types. When to Use Interfaces vs Type Aliases | Interface | Type Alias | |------------|------------| | Best for object shapes | Works for objects and primitive types | | Supports extends | Uses & for composition | | Commonly used for class contracts and API models | Commonly used for unions and complex type compositions | | Cannot directly represent union types | Can represent union types | Summary Objects, arrays, unions, intersections, tuples, enums, and interfaces are fundamental building blocks for modeling data in TypeScript.
June 10, 2026
TypeScript Compiler and tsconfig.json Explained When working with TypeScript, the TypeScript compiler (tsc) is responsible for converting TypeScript code into JavaScript. Understanding how the compiler works and how to configure it is essential for building TypeScript applications effectively. Initializing a TypeScript Project To create a TypeScript configuration file, run: This generates a file called: The tsconfig.json file contains settings that control how TypeScript compiles your code. Understanding compilerOptions Inside tsconfig.json, you'll find a section called compilerOptions. This section allows you to customize how TypeScript behaves during compilation. Compiling TypeScript Files To compile a single file: TypeScript generates a corresponding JavaScript file: Watch Mode Instead of manually recompiling after every change, you can use watch mode. or the shorter form: The compiler continues running and automatically recompiles whenever the file changes. JavaScript Is Generated Even When Errors Exist By default, TypeScript still emits JavaScript files even if compilation errors occur. To prevent this behavior, enable: Compiling an Entire Project When a tsconfig.json file exists, you can simply run: TypeScript automatically compiles all configured files in the project. Controlling Which Files Are Compiled files include exclude Output Directory The name dist stands for distribution. Target JavaScript Version | Target | Description | |----------|----------| | ES5 | Older browser compatibility | | ES2015 (ES6) | Modern JavaScript features | | ES2020 | Widely used modern target | | ESNext | Latest supported JavaScript syntax | The any Type Here, name is implicitly assigned the type any. noImplicitAny Now TypeScript reports an error when a parameter implicitly becomes any. Recommended Beginner Configuration Summary The TypeScript compiler converts TypeScript into JavaScript and is controlled through the tsconfig.json file. Understanding options such as target, outDir, include, exclude, noEmitOnError, and noImplicitAny will help you build TypeScript projects with better structure, safer code, and a smoother development experience.
June 11, 2026
TypeScript and the DOM: Type Assertions, Declaration Files, and Working with Browser APIs One of the biggest advantages of TypeScript is that it understands many JavaScript environments out of the box. For example, when writing code in a browser, TypeScript already knows about objects such as document, window, Math, and many other browser APIs. This knowledge comes from TypeScript's built-in type declaration files. How Does TypeScript Know About document? Consider the following code: Even though we never defined document, TypeScript provides autocomplete and type checking for it. The lib Option in tsconfig.json Inside tsconfig.json you'll find a compiler option called lib. These libraries tell TypeScript which built-in APIs should be available. If you remove DOM from the list, TypeScript no longer knows what document is. What Are Declaration Files? TypeScript understands JavaScript code through declaration files. A declaration file contains type information only. The actual implementation exists elsewhere, usually in the browser or a JavaScript library. Why Are Declaration Files Important? Declaration files become especially important when publishing libraries. This allows consumers to get autocomplete, type checking, and editor support. Understanding getElementById TypeScript infers: because the element may not exist. Non-Null Assertions If you know an element definitely exists: The ! tells TypeScript that the value is not null. Type Assertions A type assertion tells TypeScript to treat a value as a specific type. This only changes TypeScript's understanding of the value. Working with HTMLInputElement Now TypeScript understands that input is an input element and allows access to: without errors. Handling Form Submissions By default, HTML forms: 1. Send a GET request. 2. Refresh the page. To prevent this behavior: preventDefault() stops the browser from performing the default form submission. Summary TypeScript understands browser APIs through built-in declaration files and configured libraries. The lib option controls which APIs are available, while .d.ts files describe the shape of JavaScript code without containing implementations. When working with the DOM, you'll frequently encounter nullable values and generic element types. Features such as non-null assertions (!) and type assertions (as) help TypeScript understand your intent and provide safer access to browser APIs while maintaining strong type checking.