Level up your JavaScript: arrow functions, array methods, destructuring, spread, classes, and errors.
You can already write JavaScript that works. This course teaches the JavaScript that other people write, so you can read any codebase and recognise what you are looking at. Arrow functions, the map and filter and reduce that replace half your loops, the destructuring and spread that reshape data in one line, the classes that stamp out objects, and the try and catch that keep bad input from taking a program down.
One idea runs from the first item to the last: a function is a value. Once you can hand a function to another function, array methods stop being magic, and you will know that for certain because you build map and filter yourself, by hand, before meeting the real ones. From there the data gets richer, the objects start carrying their own behaviour, and the programs learn to defend themselves.
Everything happens in one place: the Depot, a small warehouse inventory of five products. Every section works the same records, so your attention goes to the new idea rather than to new fixture data. You ship four programs from it, a stock report, an order builder, a product catalogue, and the Depot Manager capstone, where classes, array methods, and error handling run as one machine. Finish everything and your certificate is waiting.
56 Lessons • 59 Practices • 18 Quizzes • 4 Projects · ~11h Total
Not just theory. You finish this course with real work to show.
This is the same in-browser editor every lesson uses. Edit the code, hit Run.
Run code in the browser and see the result immediately. Every lesson works this way.
Stuck? Puff explains the error and nudges you forward, without giving the answer away.
Streaks, diamonds, and certificates. Your progress saves automatically, forever.
Every completed course issues a certificate with a public verification link.
Every certificate has a public verification link employers can check.
One certificate per course. Finish a program and earn its program certificate too.
LinkedIn-ready, with a PDF you can download and attach.
Your loops work. These are the idioms that replace half of them, and the ones job listings mean by "modern JavaScript".
React is arrows, map, destructuring, and spread on every line. Learn them calmly here, before a framework is also in the way.
Array methods are the interview dialect. This course makes them the way you naturally reach for data.
Intermediate JavaScript is free to start, no credit card needed. Some later sections are part of Pro, and finishing every section, including the certificate, needs a Pro plan.
Yes, or its ground: variables, functions, if and else, arrays, loops, and objects. This course spends all of them from item one and never re-teaches them. If you can write a for loop over an array without looking it up, you are ready.
Same language, different altitude. Basics taught you to make a program work. This course teaches the idioms that make it short, readable, and safe, which are the ones you will meet in real projects and in every job interview. It is still console-only: pages and clicks belong to JavaScript DOM.
No. Everything runs in your browser on Devpuff: write JavaScript in the editor, press Run, and the console answers instantly.
Four programs from one warehouse dataset: a stock report built on map, filter, and reduce, an order builder that reshapes data without ever changing the original, a product catalogue built on classes, and the Depot Manager capstone, which refuses invalid input with real error handling.
No, and that is deliberate. Waiting for answers over a network is a genuinely separate subject with its own habits, and cramming it in beside array methods teaches neither well. It has its own course, Async JavaScript. Everything in Intermediate JavaScript runs instantly and in order.
Yes. Finish every item in Intermediate JavaScript and Devpuff issues a course certificate with a public link that anyone can verify.
How this course connects to the bigger picture, and what to explore next.
Data structures and algorithms in JavaScript: Big O, stacks, queues, linked lists, searching, and sorting.
Make pages react: select elements, handle events, read input, and build the page from your data.
Write real web pages by hand: document structure, text, links, lists, images, semantic HTML, and forms.
Free to start, no credit card required. Write real code from the first lesson and keep your progress forever.
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