maybe-monad.js

function Nothing() {}

function Just(x) {
    this.x = x;
}

function divide(a, b) {
    if (typeof a !== 'number' || typeof b !== 'number' || b === 0) {
        return new Nothing();

    } else {
        return new Just(a / b);
    }
}

function unit(x) {
    if (x === null || x === undefined) {
        return new Nothing();

    } else {
        return new Just(x);
    }
}

function bind(mx, fn) {
    if (mx instanceof Nothing) {
        return new Nothing();

    } else {
        return fn(mx.x);
    }
}


function mdivide(ma, mb, mc) {
    return bind(ma, a => {
        return bind(mb, b => {
            return bind(divide(a, b), tmp => {
                return bind(mc, c => {
                    return divide(tmp, c);
                });
            });
        });
    });
}