Is it possible to get an "inverse" function of a Boolean function in javascript?

I was looking to write an "all-or-nothing" function over an array. One approach is, of course, to leverage Array.prototype.every and do something like

function allOrNothing(arr, f, fInv) {
  return arr.every(f) || arr.every(fInv);
}

where f and fInv are indicator functions, and fInv is an "inverse" function of f. For example, if f = (x) => x != null, then fInv = (x) => x == null.

This leads me to think: is it possible to get the function fInv from f?

>Solution :

This function, given a function f as an input, returns its boolean inverse:

let invert = (f) => (x) => !f(x)

e.g.

let invert = (f) => (x) => !f(x)

let eq_five = (x) => x == 5
let neq_five = invert(eq_five)

console.log(eq_five(5)) // true
console.log(neq_five(5)) // false