The language of the web — fundamentals, the DOM, and patterns.
JavaScript is what makes web pages interactive. Learn what it is, how it differs from HTML and CSS, how to add it to a page, and write your first lines of real code — explained simply, from zero.
Variables store information in your code, and data types describe what kind of information it is. Learn let, const, and var, plus strings, numbers, booleans, and the other core JavaScript types.
Operators let you calculate and compare values; conditionals let your code choose what to do. Learn arithmetic and comparison operators, if/else if/else, logical operators, and the ternary shortcut.
Functions package code into reusable, named blocks you can run anytime. Learn how to declare functions, pass in parameters, return values, and use modern arrow functions — the heart of organized code.
Arrays hold ordered lists; objects hold labeled groups of values. Learn how to create, access, and modify both — the two structures behind nearly all real-world JavaScript data.
Loops run the same code many times — perfect for going through arrays. Learn the for loop, while loop, the modern for...of, and array methods like forEach and map that make iteration clean.
The DOM is how JavaScript connects to your HTML — selecting elements, changing text and styles, and creating or removing content. Learn querySelector, textContent, classList, and dynamic updates.
Events are how your code reacts to what users do — clicks, typing, form submissions. Learn addEventListener, the event object, common event types, and build a fully interactive feature from scratch.
Strings hold every piece of text your program touches — names, messages, URLs. Learn how to create, join, search, slice, and transform strings with JavaScript's built-in methods and template literals.
JavaScript has one number type for everything — integers and decimals alike. Learn how numbers really work, the floating-point gotcha that surprises everyone, and the Number and Math tools you'll use to format, round, and calculate.
The Date object lets you create, read, format, and do math with dates and times. Learn how it really works, the timezone traps that bite everyone, and the modern way to handle dates safely.
Arrays come with dozens of built-in methods for transforming, searching, and reshaping lists. Learn the ones you'll actually use every day — map, filter, reduce, find, and friends — with clear examples.
Go beyond the basics of objects — dynamic keys, methods and this, copying versus referencing, Object.keys/values/entries, freezing, and the patterns you'll use in real code every day.
Destructuring lets you pull values out of arrays and objects into variables in a single, readable line. Learn array and object destructuring, defaults, renaming, nesting, and the patterns you'll use in real code every day.
Three dots that do two opposite jobs. Learn how the spread operator unpacks arrays and objects, how rest parameters gather extra arguments into one array, and exactly how to tell the two apart.
Scope decides which variables your code can see; closures let a function remember the variables it grew up with. Master both and a huge chunk of JavaScript stops feeling like magic.
this is the most misunderstood word in JavaScript. Learn the simple rule behind it: this is decided by HOW a function is called, not where it's written — plus arrow functions, bind, and the classic gotchas.
Hoisting explains why a function works before its definition, why a var is undefined instead of an error, and why let throws in the temporal dead zone. Understand what JavaScript actually moves to the top — and what it doesn't.
Errors are part of normal code, not a sign you failed. Learn how try...catch works, how to throw your own errors, what finally is for, and how to handle problems gracefully instead of crashing.
JSON is the format the web speaks. Learn what it is, how JSON.parse and JSON.stringify work, the gotchas around dates and undefined, and how to handle real data safely.
A Promise represents a value that isn't ready yet — like data from a server. Learn how Promises work, how to chain them with .then and .catch, and how they tame the callback mess.
async/await is syntax built on top of promises that lets you write asynchronous JavaScript in a flat, top-to-bottom style. Learn how it works, how to handle errors with try/catch, how to run tasks in parallel, and the traps to avoid.
The Fetch API is how modern JavaScript talks to servers — requesting data, sending it, and handling the response. Learn fetch with async/await, JSON, error handling, POST requests, and the gotchas that trip people up.
localStorage lets your page remember data between visits — no server required. Learn how to store, read, and remove values, why everything is a string, and the gotchas around quotas, JSON, and security.
ES modules let you break a big script into small files that export and import what they need. Learn export, import, default vs named exports, and how modules keep your code organized and free of global clutter.
Classes give you a clean way to define the shape and behavior of objects once, then stamp out as many as you need. Learn constructors, methods, getters, static members, inheritance, and private fields.
Once you know the syntax, the next step is writing JavaScript that's easy to read, hard to break, and pleasant to come back to. Here are the habits that separate messy code from solid, professional code.