# make-synchronous

> Make an asynchronous function synchronous

**This is the wrong tool for most tasks!** Prefer async APIs whenever possible.

The benefit of this package over packages like [`deasync`](https://github.com/abbr/deasync) is that this one is not a native Node.js addon (which comes with a lot of problems). Instead, this package executes the given function synchronously in a [`worker`](https://nodejs.org/api/worker_threads.html) or [`subprocess`](https://nodejs.org/api/child_process.html).

Works in Node.js only — not the browser.

## Install

```sh
npm install make-synchronous
```

## Usage

Runs in a worker thread by default:

```js
import makeSynchronous from 'make-synchronous';

const fn = makeSynchronous(async number => {
	const {default: delay} = await import('delay');

	await delay(100);

	return number * 2;
});

console.log(fn(2));
//=> 4
```

To run in a subprocess instead:

```js
import makeSynchronous from 'make-synchronous/subprocess';

makeSynchronous(async () => {
	// Runs in a subprocess.
});
```

Subprocess execution is slower, but has the benefit of full process isolation.

## API

### makeSynchronous(asyncFunction | string)

Returns a wrapped version of the given async function or a string representation to a async function which executes synchronously. This means no other code will execute (not even async code) until the given async function is done.

The function is executed in a worker or subprocess, so you cannot access variables or imports from outside its scope. Use `await import(…)` to import dependencies inside the function.

Uses [`MessagePort#postMessage()`](https://nodejs.org/api/worker_threads.html#portpostmessagevalue-transferlist) or the V8 serialization API to transfer arguments, return values, errors between the worker or subprocess and the current process. Most values are supported — except functions and symbols.

## Related

- [make-asynchronous](https://github.com/sindresorhus/make-asynchronous) - Make a synchronous function asynchronous by running it in a worker
- [sleep-synchronously](https://github.com/sindresorhus/sleep-synchronously) - Block the main thread for a given amount of time
- [make-synchronized](https://github.com/fisker/make-synchronized) - For advanced cases like fully synchronizing an existing module or needing top-level imports