AI solution for Interview Question on BFE.dev
62. What is Promise ? How to resolve a bunch of Promises in order?

A Promise is an object that represents a value that is not known yet but might be resolved in the future. It has three states: pending, fulfilled, and rejected. Promises are widely used in JavaScript for handling asynchronous operations, such as fetching data from an API.

To resolve a bunch of Promises in order, we can use Promise chaining. In this method, each Promise is linked to the next one in a chain, so that only when a Promise is resolved does the next one start to be executed.

For example, let's say we have an array of Promises called promiseArray. We can use reduce() and Promise chaining to execute them in order:

promiseArray.reduce((prevPromise, nextPromise) => {
  return prevPromise.then(() => nextPromise());
}, Promise.resolve())

Here, reduce() method is used to iterate over the promiseArray. In each iteration, the current Promise is chained to the previous Promise using then(). Promise.resolve() is used as the initial Promise for the chain.

By using Promise chaining, we can ensure that Promises are executed in the desired order and handle their results accordingly.