Converts a Node.js-style callback API to a function that returns a Promise

wrap.js

module.exports = function(fn, ctx) {
    if (!fn || !(fn instanceof Function)) throw Error('Invalid arguments');
    return function() {
        const _args = Array.from(arguments);
        var promiseFn = function(resolve, reject) {
            _args.push(function(err, data) {
                if (err) return reject(err);
                return resolve(data);
            });
            fn.apply(ctx, _args);
        };
        return new Promise(promiseFn);
    };
}

/** USAGE **/
const wrap = require('./wrap');
const fs = require('fs');

const readFile = wrap(fs.readFile, null);

readfile('./data/somefile.txt').then(function(buffer) {
    const contents = buffer.toString('ascii');
}).catch(function(error) {
   console.log(error);
});