Create an empty function

A function that does nothing and returns undefined.

JavaScriptNode.js & browsers Version 1.0.0 · MIT · .md

function noop() {}

Usage

const send = ({ onProgress = noop } = {}) => { onProgress(100); return 'sent'; };
send(); // → 'sent'
noop(); // → undefined

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

Know the limits

• A shared noop makes a safe default callback, as in send above.
• The original’s alternative, Function(), compiles code at runtime: a Content-Security-Policy without unsafe-eval, such as this site’s, blocks it.

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

• Logical xor operator — True when exactly one of two values is truthy.
• Identity function — Return the argument unchanged.
• Box handler — Chain transformations on a value, then unwrap the result.