JavaScript Fundamentals

Why modern JavaScript avoids var, and what 'hoisting' means — so old tutorials never confuse you.

Put Module 1 together: trace real mini-programs using console.log, comments, let, and const.

Create text values with strings, glue them together, and build them cleanly with template literals.

Transform text with the built-in actions every string knows: trim, toUpperCase, includes, slice, and more.

Work with integers, decimals, and JavaScript's built-in Math toolbox — and meet the famous 0.1 + 0.2 surprise.

Turn "42" into 42 and back — plus NaN, the strange value you get when a conversion fails.

The yes/no type, intentional emptiness, and the difference between null and undefined.

Master the operators that compute and assign values, including the post/pre-increment trap.

Understand why === is almost always the right choice and what type coercion does behind the scenes.

Understand the automatic type conversions behind JavaScript's most famous surprises — and how to stay in control.

Combine yes/no conditions with &&, ||, and !, and learn which values JavaScript treats as true or false.

The secret second life of && and || — plus ??, the modern operator for safe default values.

Branch your code based on conditions — the most fundamental control structure in programming.

Handle multiple discrete cases cleanly with switch/case — and master the fall-through mechanic.

Write concise inline conditionals with the ternary operator — and learn when NOT to use it.

Apply if/else, switch, and the ternary to realistic scenarios — and learn which tool fits which job.

Meet the array — JavaScript's list — just enough to start looping over collections of values.

Repeat code a fixed number of times with the classic for loop — the workhorse of iteration.

Loop when you don't know the count upfront — and the key difference between while and do-while.

Iterate arrays with for...of and object keys with for...in — cleaner than index-based loops.

Classic loop exercises — running totals, countdowns, filtering — including your first FizzBuzz.

Define and call functions, understand return values, and learn the difference between declarations and expressions.

Global vs local variables, why functions can see out but you can't see in, and a first glimpse of closures.

Store functions in variables, pass them around like data, and learn why declarations can be called 'early' but expressions can't.

Write functions in a shorter syntax and understand how arrow functions handle `this` differently.

Handle missing arguments gracefully, collect any number of parameters, and expand arrays into arguments.

Trace, complete, and choose between functions — declarations, arrows, defaults, rest, and scope, all together.

A proper foundation: create, read, update, and search arrays — including includes, indexOf, and find.

Grow and shrink arrays with push, pop, shift, unshift, and splice — and learn what 'mutation' really means.

The non-mutating toolkit — slice, concat, join, spread copies — plus sort and its infamous default behaviour.

Transform every element with map and keep only what passes with filter — the two most-used array methods in JavaScript.

The most powerful — and most feared — array method, built up slowly from the running-total loop you already know.

Unpack array values into variables with destructuring and clone/merge arrays with spread.

Model real-world entities with key-value pairs, dynamic property access, and Object utility methods.

Why copying an object doesn't really copy it, why identical objects aren't ===, and how to make true copies.

Turn any object into arrays of keys, values, or pairs — and loop over objects with all your array skills.

Add methods to objects, understand `this`, and unpack values with object destructuring.

Unpack object properties into variables — with renames and defaults — and reach into maybe-missing data safely with ?.

Why JavaScript can't just wait, what setTimeout reveals about the language, and how callbacks schedule work for later.

Represent future values with Promises, chain .then(), and handle errors with .catch().

Write asynchronous code that reads like synchronous code using async functions and the await keyword.

Make HTTP requests to REST APIs using fetch, read JSON responses, and handle network errors.

Read a complete, realistic mini-app that uses everything you've learned — then take a look at where to go next.