Wrap a callback and return a promise

wrapcallbackinpromise.js

function doThingThatReturnsPromise(arg1) {
    return new Promise(function(resolve, reject) {
        fnThatDoesTheThingButAcceptsACallback(arg1, function callback(err, result) {
            if(err) {
                // the callback was called with an error
                return reject(err);
            }
            // the callback was called with a result
            resolve(result);
        });
    });
}

// cool es6 function version
function doThingThatReturnsPromiseES6(arg1) {
    return new Promise((resolve, reject) => {
        fnThatDoesTheThingButAcceptsACallback(arg1, (err, result) => {
            err && reject(err) || resolve(result);
        });
    });
}