Learn
Guides for the playground
Original articles that explain how Code Arena works — and how to get more out of JavaScript, TypeScript, and Python online. Prefer a runnable snippet? Open the examples library.
JavaScript TypeError: X is not a function
Fix TypeError: X is not a function in a free online JavaScript compiler. Learn why the value is not callable, how to inspect it, and how to repair the call without rewriting the whole file.
Updated August 22, 2026JavaScript ReferenceError and undefined, explained
Tell ReferenceError apart from an undefined value. Fix missing names in a free online JavaScript compiler — no account and no Node install required.
Updated August 22, 2026Python IndentationError: how to fix it online
Fix IndentationError and unexpected indent in Python. See a broken block, correct the spaces, and run it in Code Arena without installing Python locally.
Updated August 22, 2026Python NameError: name is not defined
Fix NameError in Python when a variable or function is not defined. Run a tiny example online and read the traceback without a local install.
Updated August 22, 2026Python TypeError: what it means and how to fix it
Read Python TypeError messages for bad operands, missing arguments, and None. Fix a small example in the online compiler without installing Python.
Updated August 22, 2026Run JavaScript online without installing Node
Run JavaScript in the browser with a free online compiler. No Node install, no signup, no project folder — write, run, and read output in one tab.
Updated August 22, 2026Online Python compiler vs local install
When to use a free online Python compiler and when to install Python locally. Try a snippet in Code Arena first — no virtualenv required.
Updated August 22, 2026What is a JavaScript AST?
An abstract syntax tree is how parsers see your JavaScript. Learn the idea, then open Code Arena’s AST tab — a free visualizer with no signup.
Updated August 22, 2026How the JavaScript AST view works in Code Arena
A practical guide to abstract syntax trees: what they are, how Code Arena builds one from your JavaScript, and how pan, zoom, and node selection help you learn syntax.
Updated July 19, 2026Running TypeScript online with Node type stripping
How Code Arena executes TypeScript with Node.js type stripping — what works, what does not, how it differs from tsc, and how to design playground-friendly typed snippets.
Updated July 19, 2026What a sandboxed online compiler actually does
A clear look at how browser editors talk to isolated runtimes — why sandboxes matter for safety, what limits you will hit, and how Code Arena’s model fits teaching and everyday experiments.
Updated July 19, 2026JavaScript console basics in the browser playground
How to print values, structure debug output, and read the Output panel in Code Arena’s JavaScript editor — with habits that transfer to Node and browsers.
Updated July 19, 2026Reading JavaScript errors without guessing
A practical field guide to SyntaxError, ReferenceError, TypeError, and stack traces in Code Arena — so you fix the first real problem instead of rewriting everything.
Updated August 22, 2026Sharing code snippets safely (what URLs expose)
How Code Arena share links work, what they encode, how URLs leak through chat and history, and a practical checklist before you hit Share.
Updated July 19, 2026Python online: common beginner errors and fixes
Fix IndentationError, NameError, TypeError, SyntaxError, and loop timeouts quickly in Code Arena’s Python editor — with a traceback-reading habit that scales.
Updated August 22, 2026Online compiler vs local setup: when to use which
A practical comparison of playgrounds like Code Arena and a local Node/Python install — so you pick the right environment for learning, debugging, and real projects.
Updated August 22, 2026Timeouts and rate limits in an online playground
Why Code Arena limits run time and request frequency, how those limits show up when you code, and how to rewrite snippets so they finish cleanly.
Updated July 19, 2026Debugging with small experiments
A method for isolating bugs in online compilers: shrink the program, form a hypothesis, change one variable, and keep a trail of what you learned.
Updated July 19, 2026