Functions as sets in Javavscript

set.js

const emptySet = () => false;

const addElement = (set, element) => {
	return (item) => (item === element ? true : set(item));
};

const removeElement = (set, element) => {
	return (item) => (item === element ? false : set(item));
};

// Create a set containing 1,2,3
let mySet = emptySet;
mySet = addElement(mySet, 1);
mySet = addElement(mySet, 2);
mySet = addElement(mySet, 3);

// Test for presence of 3 and 4
console.log(mySet(3)); // true
console.log(mySet(4)); // false

// Remove 1 from set
mySet = removeElement(mySet, 1);
console.log(mySet(1)); // false