Blog
Mert Özen's blog posts on software development, backend, frontend, and DevOps.
What Is JavaScript? How It Runs in the Browser, ECMAScript and Your First Line
We learn JavaScript's place on a web page, how ECMAScript and TC39 evolve the language and what browser engines do, then write our first lines in the console and change a page live.
Your First JavaScript Script: The script Tag, defer, async and DevTools
We link JavaScript to HTML inline and as an external file, see how defer and async differ, and try console methods, reading error messages and our first breakpoint in DevTools.
JavaScript Variables: let and const, Block Scope and the TDZ
We declare variables with let and const, and use examples to see reassignment versus mutation, block scope, naming rules, why var has been retired, and the TDZ.
JavaScript Data Types: Primitives, Objects and typeof
We meet JavaScript's seven primitive types and objects, and use examples to see why typeof says "object" for null, why primitives are immutable, and how values differ from references.
JavaScript Operators: Arithmetic, Equality, Logical Operators and Truthy/Falsy
We cover arithmetic and assignment operators, comparisons, == versus === and coercion, truthy/falsy values, short-circuiting with && and ||, the ?? operator and precedence pitfalls.
JavaScript Conditionals: if/else, the Ternary Operator and switch
We use examples to cover if/else if/else chains, the ternary operator, fall-through and break in switch, truthy/falsy traps in conditions, the early return idea and writing readable conditions.
JavaScript Loops: for, while, for...of and for...in
We use examples to cover for, while and do...while loops, for...of for arrays and strings, for...in for objects, break and continue, and the infinite loop trap that locks up the tab.
JavaScript Strings: Template Literals, String Methods and Immutability
From quote types and template literals to at(), slice, includes, replaceAll, split and padStart, we learn how strings work, why they are immutable, and the Turkish İ and emoji length traps.
JavaScript Number and Math: 0.1 + 0.2, Number Conversion, Random Numbers and Formatting
We learn JavaScript's single number type, the 0.1 + 0.2 precision issue, Number vs parseInt, NaN and bigint, rounding and random numbers with Math, and currency formatting with Intl.NumberFormat.
JavaScript Arrays: push, pop, slice, splice, Spread and the sort Trap
We learn how to create arrays, access them with at(), push/pop/shift/unshift, slice vs splice, copying with spread, forEach, why sort gets numbers wrong, and the reference trap.
JavaScript Functions: Declarations, Arrow Functions, Parameters and return
We learn function declarations, expressions and arrow functions, parameters and arguments, default parameters, return, passing functions as callbacks, function scope and how to write good functions.
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.