Tail Call Optimization

tailCall.js

// http://paulbutler.org/archives/tail-recursion-in-python/

function tailCall(fn) {
    return function () {
        fn = fn.apply(this, arguments);
        while (typeof fn === 'function') {
            fn = fn();
        }
        return fn;
    };
}

var tailEven,
    tailOdd;

tailEven = function (x) {
    if (x === 0) {
        return true;
    } else {
        return function () {
            return tailOdd(x - 1);
        };
    }
};

tailOdd = function (x) {
    if (x === 0) {
        return false;
    } else {
        return function () {
            return tailEven(x - 1);
        };
    }
};

var even = tailCall(tailEven);
var odd = tailCall(tailOdd);

console.log(even(100));
console.log(odd(100));