JS callback functions and promises chaining

promises.js

"use strict";

var typicalCallbackFunction = function(argument, callback) {
    argument = '<' + argument + '>';
    callback(null, argument);
}

var promisifiedTypicalCallbackFunction = (argument) => new Promise((resolve, reject) => {
    typicalCallbackFunction(argument, (err, result) => err ? reject(err) : resolve(result));
});

var async1 = (arg) => new Promise((resolve, reject) => {
    setTimeout(f => resolve('[' + arg + ' async1]'), 100);
});

var async2 = (arg) => new Promise((resolve, reject) => {
    setTimeout(f => resolve('[' + arg + ' async2]'), 200);
});

promisifiedTypicalCallbackFunction('pcf')
.then(th => async1(th + '...'))
.then(async2)
.then(console.log);