Advanced promise flow examples

let now = Date.now(); //// - advanced promise flow examples - // - setup - // resolves with the value 5 let completedSoon = Promise.resolve(5).then((res) => { console.log(`${Date.now() - now}: completedSoon done`); return res; }); // completes after completedSoon let pDelayed = new Promise((resolve, reject) => { console.log(`${Date.now() - now}: timeout promise created`); setTimeout(() => { console.log(`${Date.now() - now}: timeout completed`); resolve(); }, 2000); }); // - examples - // lets then() on completed soon AFTER it has been completed let properPromise = pDelayed .then(() => completedSoon) .then((res) => console.log(`${Date.now() - now}: then(() => completedSoon): ${res}`)); // res is 5 as expected // doing the following could be hard to debug and is incorrect let improperPromise = pDelayed .then(completedSoon) // instead of () => completedSoon // DONT do this ^^^, IMO it should throw an error, maybe there is a good reason it doesnt though // I tested it and it also doesnt actually wait on completedSoon .then((res) => console.log(`${Date.now() - now}: then(completedSoon): ${res}`)) // res is undefined // we can also then() on completedSoon multiple times! (and use pDelayed multiple times) let properPromise2 = pDelayed .then(() => completedSoon) .then((res) => console.log(`${Date.now() - now}: #2 then(() => completedSoon): ${res}`)); // res is 5 as expected //// - end of examples - // runkit auto logs the last defined object so lets await so our logs are not dirtied with a print out of order await properPromise2; // runkit lets you await outside of a user defined async, which is kind of dangerous i suppose, // but can be useful for testing let _ingnoreThis = "";