JSFiddle - React, Tailwind, and code Playground

by ciju

JavaScript

var s3 = function (h) {
    return (function (f) { // sum function
        return function (n) { 
            return n === 1 ? 1 : n + f(n - 1);
        };
    })(function (n) {
        return h(h)(n);
    });
}
console.assert(s3(s3)(5) === 15, s3(s3)(5));