recursion.js

#!/usr/bin/nodejs
'use strict'

let factorial = (n) =>
    n === 0 ?
    1 :
    n * factorial(n-1)

let tail_factorial = (n) => {
    let part_factorial = (n, acc) =>
        n === 0 ?
        acc :
        part_factorial(n-1, n*acc)
    return part_factorial(n, 1)
}

let look_ma_no_curly_braces = (n) => (
    f => f(f, n, 1)
)(
    (f, n, acc) =>
        n === 0 ?
        acc :
        f(f, n-1, n*acc)
)

console.log(factorial(5))
console.log(tail_factorial(7))
console.log(look_ma_no_curly_braces(10))