https://learn-javascript.org/ Free JavaScript tutorials with a runnable console, plus AI-native workflow guides for JS projects. Sun, 06 Sep 2026 03:07:12 GMT https://learn-javascript.org/hello-world/https://learn-javascript.org/hello-world/Welcome to the first tutorial. In this tutorial you will learn how to write your first line of code. JavaScript is a very powerful language. https://learn-javascript.org/ai/agent-setup/https://learn-javascript.org/ai/agent-setup/Node projects have the loosest defaults of any ecosystem here, which means the setup work matters more. https://learn-javascript.org/review/failure-modes/https://learn-javascript.org/review/failure-modes/Async is where most of it lives. The rest is stale idioms from a decade of training data written before the language got good. https://learn-javascript.org/variables-and-types/https://learn-javascript.org/variables-and-types/JavaScript is dynamically typed, so a variable can hold any value. Declare with const by default, let when you need to reassign. https://learn-javascript.org/arrays/https://learn-javascript.org/arrays/JavaScript can hold an array of variables in an Array object. In JavaScript, an array also functions as a list, a stack or a queue. https://learn-javascript.org/review/dependencies/https://learn-javascript.org/review/dependencies/npm is the largest supply-chain surface in software, and the only major ecosystem where installing a package runs arbitrary code before you have written a line. https://learn-javascript.org/ai/agents-md/https://learn-javascript.org/ai/agents-md/JavaScript needs a longer instructions file than the typed languages, and most of the extra length should be one list: what the platform now does that a package used to. https://learn-javascript.org/manipulating-arrays/https://learn-javascript.org/manipulating-arrays/Arrays can also function as a stack. The push and pop methods insert and remove variables from the end of an array. https://learn-javascript.org/review/security/https://learn-javascript.org/review/security/No compiler, a dynamic object model and the largest dependency ecosystem in software. The vulnerabilities that recur in generated JS follow from all three. https://learn-javascript.org/ai/evals/https://learn-javascript.org/ai/evals/Your function is now non-deterministic, slow, costs money per call, and streams. Here is a test strategy that still works — including for the streaming part, which is where most of the real bugs are. https://learn-javascript.org/operators/https://learn-javascript.org/operators/Every variable in JavaScript is casted automatically so any operator between two variables will always give some kind of result. https://learn-javascript.org/review/performance/https://learn-javascript.org/review/performance/Node is single-threaded, so a performance bug is an availability bug. Every item here is really the same item: something blocked the event loop or ran unbounded. https://learn-javascript.org/ai/tokenomics/https://learn-javascript.org/ai/tokenomics/Node's specific cost problem is streaming: the user leaves, the stream keeps running, and you keep paying. That plus three other changes usually halves the bill. https://learn-javascript.org/conditions/https://learn-javascript.org/conditions/The if statement allows us to check if an expression is equal to true or false, and execute different code according to the result. https://learn-javascript.org/loops/https://learn-javascript.org/loops/JavaScript has two methods for running the same code several times. It is mainly used for iterating over arrays or objects. https://learn-javascript.org/objects/https://learn-javascript.org/objects/JavaScript is a functional language, and for object oriented programming it uses both objects and functions, but objects are usually used as a data structure, similar to a dictionary in Python or a map in Java. https://learn-javascript.org/functions/https://learn-javascript.org/functions/Functions are code blocks that can have arguments, and function have their own scope. https://learn-javascript.org/pop-up-boxes/https://learn-javascript.org/pop-up-boxes/There are three types of pop-up boxes in javascript: confirm, alert, and prompt. https://learn-javascript.org/callbacks/https://learn-javascript.org/callbacks/Callbacks in JavaScript are functions that are passed as arguments to other functions. https://learn-javascript.org/arrow-functions/https://learn-javascript.org/arrow-functions/Arrow functions are a feature of ES6, their behavior are generally the same of a function. https://learn-javascript.org/object-oriented-javascript/https://learn-javascript.org/object-oriented-javascript/JavaScript uses functions as classes to create objects using the new keyword. https://learn-javascript.org/function-context/https://learn-javascript.org/function-context/Functions in JavaScript run in a specific context, and using the this variable we have access to it. https://learn-javascript.org/inheritance/https://learn-javascript.org/inheritance/JavaScript uses prototype based inheritance. https://learn-javascript.org/destructuring/https://learn-javascript.org/destructuring/Destructuring is a feature of ES6, introduced for making easier and cleaner some repetitive operations and assignments made in JS. https://learn-javascript.org/promises-and-async-await/https://learn-javascript.org/promises-and-async-await/The single most important topic in modern JavaScript, and the one where generated code most often gets it subtly wrong. https://learn-javascript.org/modules/https://learn-javascript.org/modules/How JavaScript code is split across files — and the CommonJS/ESM split that still causes more confusion than anything else in the ecosystem. https://learn-javascript.org/error-handling/https://learn-javascript.org/error-handling/Throwing, catching, and the specific ways JavaScript error handling goes wrong — including the one that terminates your process. https://learn-javascript.org/closures-and-scope/https://learn-javascript.org/closures-and-scope/The mechanism behind callbacks, module privacy, React hooks and most memory leaks. Worth understanding properly once. https://learn-javascript.org/tensorflow-js/https://learn-javascript.org/tensorflow-js/TensorFlow.js is an open-source hardware-accelerated JavaScript library for training and deploying machine learning models. https://learn-javascript.org/tensorflow-cnns/https://learn-javascript.org/tensorflow-cnns/Master computer vision with CNNs using TensorFlow.js.