Blog
Mert Özen's blog posts on software development, backend, frontend, and DevOps.
Basic and Special Types in TypeScript: any, unknown, never and void
Alongside string, number, boolean, bigint and symbol, we look at null and undefined in strict mode, why any is dangerous, how unknown makes it safe, and what void and never mean.
Type Inference and Annotations in TypeScript: When Do You Write the Type Yourself?
How TypeScript infers types on its own, the widening difference between let and const, why parameters get annotations, and when you should write a return type explicitly, with examples.
Setting Up TypeScript: Running Code Is Not the Same as Type-Checking It
The TypeScript Playground, installing with npm, tsc --init, npx tsc --noEmit and node file.ts on Node 26: why running code doesn't mean type-checking it, and how to read your first error message.
What Is TypeScript and Why Does It Exist? The Type Layer on Top of JavaScript
We look at the type layer TypeScript adds on top of JavaScript, the difference between compile time and runtime, what type checking catches and what changed with TypeScript 7.
JavaScript RegEx Basics: Searching and Validating Text with Regular Expressions
We use test, match, matchAll and replace with regular expressions, learn character classes, quantifiers, groups and the g, i and m flags, write email, phone and postal code checks and meet RegExp.escape.
JavaScript Date Basics: Creating, Calculating and Formatting Dates
We see that a Date is really a timestamp, then learn how to create dates, the zero-based month trap, get/set methods, the difference between two dates and formatting with toLocaleDateString and Intl.DateTimeFormat.
The JavaScript BOM: window, location, navigator and Timers
We get to know the browser objects: the global window, location for the address, navigating with history, navigator and screen info, timers with setTimeout and setInterval, and why alert, confirm and prompt are rarely used.
JavaScript Forms: Reading Values, Handling Submit and Simple Validation
We read form values with value, checked and selectedIndex, catch the submit event, write checks for empty fields, email and length, show errors on the page and get to know HTML's built-in validation.
JavaScript Events: Handling Clicks, Keyboard and Input with addEventListener
We listen to click, input, keydown and submit events with addEventListener, and learn about target and key on the event object, preventDefault, removeEventListener and why inline onclick is discouraged.
Intro to the JavaScript DOM: Selecting, Changing and Creating Elements
We meet the DOM tree the browser builds from HTML, select elements with querySelector, see why textContent and innerHTML differ and what XSS is, then change the page live with classList and createElement.
JavaScript JSON: JSON.stringify, JSON.parse, try/catch and Deep Copies
We learn JSON's syntax rules, indentation and replacers with JSON.stringify, which values get lost, JSON.parse and revivers, catching broken JSON with try/catch, and why structuredClone wins for deep copies.
JavaScript Objects: Object Literals, Properties, Object.keys and structuredClone
We learn object literals, property access with dots and brackets, nested objects, methods and this, in and Object.keys/values/entries, for...in, shallow copies with spread and deep copies with structuredClone.