Want to truly understand how JavaScript works? Not just copy-paste code, but actually know what’s happening under the hood? These 33 concepts are the foundation. Whether you’re debugging a tricky closure, optimizing async code, or preparing for technical interviews, this is the knowledge that separates developers who struggle from those who ship with confidence.
Who Is This For?
This guide meets you where you are. Whether you’re writing your first line of JavaScript or you’ve been shipping code for years, there’s something here for you.
The 33 Concepts
Each concept builds on the others. Start from the beginning or jump to what you need. Every page includes explanations, code examples, and resources to go deeper.
[FundamentalsTypes, Scope, Closures, Call Stack, a…
Want to truly understand how JavaScript works? Not just copy-paste code, but actually know what’s happening under the hood? These 33 concepts are the foundation. Whether you’re debugging a tricky closure, optimizing async code, or preparing for technical interviews, this is the knowledge that separates developers who struggle from those who ship with confidence.
Who Is This For?
This guide meets you where you are. Whether you’re writing your first line of JavaScript or you’ve been shipping code for years, there’s something here for you.
The 33 Concepts
Each concept builds on the others. Start from the beginning or jump to what you need. Every page includes explanations, code examples, and resources to go deeper.
FundamentalsTypes, Scope, Closures, Call Stack, and how JavaScript actually executes your codeFunctions & ExecutionThe Event Loop, IIFE, Modules, and why JavaScript can be both single-threaded and non-blockingWeb PlatformDOM manipulation, HTTP requests with Fetch, and Web Workers for background processingObject-Oriented JSClasses, Prototypes, the this keyword, and how inheritance really worksAsync JavaScriptCallbacks, Promises, async/await, and patterns for handling asynchronous operationsFunctional ProgrammingPure functions, Higher-order functions, map/reduce/filter, recursion, and compositionAdvanced TopicsData structures, Algorithms, Design patterns, and writing clean, maintainable code
Created by Leonardo Maldonado and improved by hundreds of contributors worldwide. Translated into 40+ languages, making JavaScript education accessible to developers everywhere.