JavaScript Online Compiler

Write and run JavaScript instantly in a sandboxed worker on your device. Interactive Map/Set/object trees, network inspection, and smart error explanations — nothing leaves your browser.

Editor

Ctrl/Cmd + Enter to run

// Welcome! Write JavaScript and hit Run (or press Ctrl/Cmd + Enter). const langs = ["JavaScript", "TypeScript", "Python"]; langs.forEach((lang, index) => { console.log(`${index + 1}. ${lang}`); }); const profile = { name: "Ada", skills: ["js", "ts"], active: true }; console.log(profile); try { JSON.parse("{ not valid json }"); } catch (error) { console.warn("Caught expected parse error:", error.message); }

Colors:keywordfunctionvariablecall()"string"123// comment

Load an example:

Output appears here. Press Run or Ctrl/Cmd + Enter. Objects log as expandable trees.

Code runs in a sandboxed worker on your device. Nothing is uploaded. Infinite loops are stopped after 3 seconds and stack overflows are reported.

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