1.2 JavaScript
Every entry filed under JavaScript and its subtopics.
What kind of help
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
10 entries match these filters
- 0386 Install Node.js on Linux, macOS and Windows Get Node.js and npm on any desktop OS. Use a version manager (nvm or fnm) when you work on several projects, or… Beginner · Step by step · Linux, macOS, Windows Article Installing languages & tools · Node.js 15 Oct 2026
- 0320 Fix: address already in use (EADDRINUSE) Something is already listening on the port your program wants. Find the process with lsof or ss, stop it or pick another… Beginner · Fixes an error · Linux, macOS Article Networking & firewalls · Node.js · Processes & ports 15 Oct 2026
- 0319 Fix: npm ERR! EACCES permission denied npm cannot write to a directory it needs: the global install location, its cache in ~/.npm, or a node_modules owned by root.… Beginner · Fixes an error · Linux, macOS Article Common errors · Node.js 15 Oct 2026
- 0263 Build a notes REST API with plain Node.js: CRUD, validation, status codes and CORS Write a small JSON API for notes using only Node.js built-ins: create, read, update and delete, input validation, correct HTTP status codes,… Intermediate · Guided project · Any system Article Making requests · Node.js · Status codes 15 Oct 2026
- 0016 let, const and var: variables and scope in JavaScript Use const by default, let when a value must change, and avoid var. The difference is about scope: where a variable is… Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0017 JavaScript array methods cheat sheet: map, filter, reduce and friends A quick reference for the array methods you use every day, with what each one returns and whether it changes the original… Beginner · Cheat sheet · Any system Article Basics 15 Oct 2026
- 0025 Regular expressions cheat sheet (JavaScript flavor) The regex syntax you actually use, from character classes and quantifiers to groups, lookarounds and flags, with the JavaScript methods that apply… Beginner · Cheat sheet · Any system Article Basics · Basics 15 Oct 2026
- 0026 Fix: TypeError: Cannot read properties of undefined (reading ‘x’) You tried to read a property from a value that is undefined or null. Find which value is missing, then guard it… Beginner · Fixes an error · Any system Article Basics · Common errors 15 Oct 2026
- 0018 Promises and async/await explained A promise is a placeholder for a value that arrives later. async/await lets you write code that waits for promises as if… Intermediate · Explains an idea · Any system Article Async code 15 Oct 2026
- 0027 Fix: SyntaxError: Cannot use import statement outside a module The file uses ES module import syntax, but Node or the browser is loading it as a classic script or CommonJS. Tell… Intermediate · Fixes an error · Any system Article Common errors · Node.js 15 Oct 2026