function add (x, y) {
return x + y
}
function makeAdder (x, addReference) {
return function (y) {
return addReference(x, y)
}
}
const addFive = makeAdder(5, add)
const addTen = makeAdder(10, add)
const addTwenty = makeAdder(20, add)
addFive(10) // 15
addTen(10) // 20
addTwenty(10) // 30