nasync-js v0.1.1

nasync-js

What if Javascript we could write asynchronous Javascript code as if it was synchronous like you would in Python or Golang?

This repo contains a transpiler for a flavor of Javascript called n/async Javascript. Its main demo is through a Starboard in-browser Notebook plugin which introduces the nasync cell type.

Example

Input (n/async Javascript)

const websiteText = fetch("https://enable-cors.org/").text();

console.log("Website text length", websiteText.length);

// All functions become async
function identity(a) {
  return a;
}

const hello = new Promise(x => setTimeout(_ => x("Hello"), 1000))
console.log("Some print message :)")

const stillHello = identity(hello);

// The last statement is the cell return value, unless it ends with a semicolon.
stillHello + " world"

Transpiled code (vanilla JS)

(async () => {const websiteText = await (await (await fetch)("https://enable-cors.org/")).text();

  await (await console).log("Website text length", (await websiteText).length);

  // All functions become async
  async function identity(a) {
    return await a;
  }

  const hello = await new (await Promise)(await (async (x) => await (await setTimeout)(await (async (_) => await (await x)("Hello")), 1000)));
  await (await console).log("Some print message :)");

  const stillHello = await (await identity)(await hello);

  // The last statement is the cell return value, unless it ends with a semicolon.
  return { cellReturnValue: await ((await stillHello) + " world") };
})();

Output

Website text length 5716
Some print message :) 

// the cell return value
Promise<"Hello world"> 

Questions

Should I use this in production?

No. You could use it for playing around and quick experimentation in a notebook, but outside of that you should stick with writing await and async yourself. Sprinkling await everywhere in your code likely won't make it run any faster.

Any caveats?

Member access expressions are not awaited (as this leads to this issues).

// n/async javascript input
const x = myObject.a.b.c();

// Transpiled output
(async () => {const x = await (await myObject).a.b.c();
})();

// What you may expect
(async () => {const x = await (await (await (await (await myObject).a).b).c)();
})();

In practice this likely what you want, and if you do need to await member variables you can just write await yourself. I welcome a contribution which can demonstrate an edge case when this is needed (I couldn't come up with one).

So what is this good for?

Use it in Starboard Notebook, load external data and play with your data as if there's no such thing as asynchronicity.

License

MIT