Check if the code is running in NodeJS

Look for process.versions.node.

JavaScriptNode.js Version 1.0.0 · MIT · .md

function isNode() { return typeof process !== 'undefined' && process.versions?.node != null; }

Usage

isNode(); // → true

Lines marked → were executed in Node.js 22, and each result was compared with the value shown. Lines marked e.g. are illustrative.

Know the limits

• Node-compatible runtimes such as Bun also set process.versions.node, so this detects compatibility, not Node.js itself. The browser tests confirm it returns false in Chromium.
• Prefer feature detection (does the API you need exist?) over runtime detection.

The function above is the code the usage lines run. It does not validate its arguments; add checks where it receives untrusted input.

Keep exploring

• Convert Celsius to Fahrenheit — Apply the temperature conversion without rounding the result.
• Convert hex to RGB — Expand #rgb if needed and read the red, green and blue channels.
• Convert URL parameters to object — Read a query string into an object; repeated keys become arrays.