How a promise library decides If it has a .then function – that’s the only standard promise libraries use. The Promises/A+ specification has a notion called thenable which is basically “an object with a then method”. Promises will and should assimilate anything with a then method. All of the promise implementation you’ve mentioned do this. … Read more
Update, you probably want to use the built-in native Promise.allSettled: Promise.allSettled([promise]).then(([result]) => { //reach here regardless // {status: “fulfilled”, value: 33} }); As a fun fact, this answer below was prior art in adding that method to the language :] Sure, you just need a reflect: const reflect = p => p.then(v => ({v, status: … Read more
The deferred antipattern (now explicit-construction anti-pattern) coined by Esailija is a common anti-pattern people who are new to promises make, I’ve made it myself when I first used promises. The problem with the above code is that is fails to utilize the fact that promises chain. Promises can chain with .then and you can return … Read more
Break the chain When you need to access the intermediate values in your chain, you should split your chain apart in those single pieces that you need. Instead of attaching one callback and somehow trying to use its parameter multiple times, attach multiple callbacks to the same promise – wherever you need the result value. … Read more