Flip the arguments of a function

JavaScript

// Reverse the order of arguments
const flip =
  (fn) =>
  (...args) =>
    fn(...args.reverse())

// For binary functions
const flip = (fn) => (b, a) => fn(a, b)

// Or for curried functions
const flip = (fn) => (b) => (a) => fn(a)(b)

Examples

const isParent = (parent, child) => parent.children.includes(child)
const isChild = flip(isParent)