Async JS is Stackless

StackGC.js

// StackGC
// =======
const StackGC = async () => null;


// Tests
// =====
// util
function assert(assertion, msg) {
    console.assert(assertion, `%s`, msg);
}


// 1. Simple recursion
// ===================
// recursive factorial
async function fact(n) {
    n = BigInt(n);

    if (n < 2)
        return 1n;

    await StackGC();
    return n * await fact(n - 1n);
}

// non-recursive factorial
function fact2(n) {
    n = BigInt(n);

    let f = 1n;
    while(n > 1)
        f *= n--;

    return f;
}

assert(
    await fact(10000) === fact2(10000),
    `fact(10000)`
);


// 2. Mutual recursion
// ===================
async function isEven(x) {
    if (x === 0)
        return true;

    await StackGC();
    return await isOdd(x - 1);
}

async function isOdd(x) {
    if (x === 0)
        return false;

    await StackGC();
    return await isEven(x - 1);
}

assert(
    await isEven(20000) === true,
    `isEven(20000)`
);

assert(
    await isOdd(20001) === true,
    `isOdd(20001)`
);