Flip the arguments of a function

Call a function with its arguments in reverse order.

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

function flip(fn) { return (...args) => fn(...args.reverse()); }

Usage

const divide = (a, b) => a / b;
flip(divide)(2, 10); // → 5
const isMember = (list, item) => list.includes(item);
flip(isMember)('ana', ['ana', 'rui']); // → true

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

• All arguments are reversed. For two arguments, (b, a) => fn(a, b) is the explicit form.

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.