parallel versus sequential promises in Javascript

parallel.js

//  jr
//  parallel versus sequential promises in Javascript
//  22.02.2022
const parallel = true;
const startTime = performance.now();
console.clear();

const asyncTimeout = (delay, data) => (new Promise(resolve => { setTimeout(() => resolve(delay, data), delay) })).then(d => `Waited ${d} seconds`);
const asyncFetch = (url) => fetch(url).then(response => (response.text())).then(text => `Fetched ${url}, and got back ${text}`);
const runTask = (spec) => (spec.task === 'wait') ? asyncTimeout(spec.duration) : asyncFetch(spec.url);
const asyncThingsToDo = [
    { task: 'wait', duration: 1000 },
    { task: 'fetch', url: 'https://jsonplaceholder.typicode.com/todos/2' },
    { task: 'wait', duration: 2000 },
    { task: 'fetch', url: 'https://jsonplaceholder.typicode.com/todos/1' },
];

if (parallel) {
    const tasks = asyncThingsToDo.map(runTask); // Run all our tasks in parallel.
    const results = await Promise.all(tasks);   // Gather up the results.
    results.forEach(x => console.log(x));       // Print them out on the console.
} else {//sequential:
    const starterPromise = Promise.resolve(null);
    const log = result => console.log(result);
    await asyncThingsToDo.reduce((p, spec) => p.then(() => runTask(spec).then(log)), starterPromise);
}
console.log(`Task finished in ${Number.parseInt(performance.now() - startTime)} miliseconds `);