Docs
How JSpark works, one page at a time. New to it? Start with your first Run.
Start here
Install JSparkWhat you need, and how to download it for Mac or Windows.Open JSpark the first timeGet past your system’s first-launch check, and what you see then.Your first RunOpen a Starter, press ⌘↵, and read what the code did.A tour of the windowThe rail, tabs, code, output and footer, and what each is for.Where your work goesTabs come back after a relaunch; in JSpark+, the Library keeps what you choose.
Guides
Try an npm packageFind a package on npm, add it with JSpark+, and call it in a Snippet.Find why a loop gives the wrong answerPeek at the value, then replay the loop one Step at a time.Try a React componentStart from the React Starter and see the page beside the code.Try out TypeScript typesSee the types as you write, and what a type error does to a Run.Test code that reads files or calls an APIRun code that reaches outside JSpark, knowing what it can reach.
Everyday
Run and Run as you typeRun on demand, or as you type, with older output marked stale.The consoleWhat a Run printed, its errors, and the last value.PeekAdd //? to a line to see the value it came to.Tabs and the Home screenOpen, name, move and close Snippets.The editorSuggestions, types on hover, mistakes underlined, Format Code.
Timeline
Step Run and the TimelineReplay a Node Run one Step at a time.Moving through StepsStep, scrub, or let Autoplay play them.VariablesEvery value at the Step, and what changed.The Call StackJSpark+See which call each Step belongs to.Step DetailLines, or Inside lines (JSpark+) for every call and loop check.What is not recordedWhat a Trace leaves out, and a Trace that ran out of room.
Pages and packages
Web pagesParts, the page beside the console, and a page that froze.Tailwind CSSTurn Tailwind on with one line of CSS; JSpark builds it, offline.StartersThe 16 ways to begin a Snippet (two need JSpark+), from Node.js to Canvas.PackagesFind a package on npm and read about it.JavaScript and TypeScriptPick a Language; TypeScript is checked as you type.A page with a serverJSpark+A page with a server Part, which it reaches with fetch.
Keeping code
Settings and looks
SettingsEvery setting, what it changes and its default.Themes and fontsApp Themes, Code Themes, fonts and text size.LayoutSide by Side or Stacked, and the output beside the code.Time and memory limitsWhy a Run was stopped, and how to give it more.The Working FolderWhere a Node Run starts, and how to open or empty it.Reset or remove JSparkRestore the default settings, or take the app off your computer.
Troubleshooting
My code did not run as I typedA Snippet that reaches outside JSpark waits for you to press Run.My TypeScript did not run because of a type errorWith “Don’t run with type errors” on, a type error stops a TypeScript Run.require or import gives an errorThe Snippet runs as a Module or a Script, and the code expects the other.My Run was stoppedIt went over the time or memory limit.My page is blank or frozeWhat to check when a Web Snippet shows nothing or stops.My Tailwind classes do nothingThe stylesheet needs the Tailwind line, and class names must be written whole.A package will not install or workInstalls need a connection; some packages need a setup step.The Library could not be readWhat the message means, and how to get your Saved Snippets back.JSpark will not openWhat to try when the app does not start.
Reference
Keyboard shortcutsEvery shortcut, on Mac and on Windows.The words JSpark usesSnippet, Run, Step, Kind and the rest, each in one line.Which Node and which browserThe versions JSpark runs your code on, and what each gives you.Outside AccessWhat counts as reaching outside JSpark, and what it does not mean.Load ModeModule or Script, and the button that switches them.Offline and privacyWhat works with no connection, and what goes online.UpdatesHow the app updates itself, in both editions.