upsync

UpSync: Callback -> Async/Await

Note: This module is intended to be used with Node.js 7+ or other JavaScript engines/transpilers that have support for ES2017 async/await.

This project is more my personal tool for learning Node.js support for JavaScript ES2017 async/await.

I thought it would be a fun exercise to write my own utility that takes a traditional callback-style function, and returns it wrapped in an async function. This is similar to some of the callback-to-promise utilities that are in various libraries.

Basic usage:

const upsync = require( "upsync" );
 
// The old, callback way of doing things
function oldSchool( firstname, lastname, callback ) {
    const msg = `kicking it old school, eh ${ firstname } ${ lastname }?`;
    callback( null, msg );
}
 
// upsync that sucker
const asyncSchool = upsync( oldSchool );
 
// Let's use it
async function runThisThang() {
    const response = await asyncSchool( "Old", "Dawg" );
    console.log( response );
}
 
runThisThang();

Same deal, but with fat arrows:

const upsync = require( "upsync" );
 
// The old, callback way of doing things
const oldSchool = ( firstname, lastname, callback ) => {
    const msg = `kicking it old school, eh ${ firstname } ${ lastname }?`;
    callback( null, msg );
};
 
// upsync that sucker
const asyncSchool = upsync( oldSchool );
 
// Let's use it
const runThisThang = async () => {
    const response = await asyncSchool( "Old", "Dawg" );
    console.log( response );
}
 
runThisThang();

Okay, here's a slightly more legitimate example

const upsync = require( "upsync" );
const fs = require( "fs" );
const readFile = upsync( fs.readFile );
 
const readAndParseJsonFile = async filename => {
    try {
        const contents = await readFile( filename );
        return JSON.parse( contents );
    } catch( err ) {
        console.log( err );
        throw err;
    }
};
 
const main = async () => {
    try {
        const pkg = await readAndParseJsonFile( "./package.json" );
        console.log( pkg );
    } catch ( err ) {
        console.log( "error in main:", err );
    }
}
 
// async functions return a promise
main().then( () => {
    console.log( "finished!" );
} );