How to Synchronize a Sequence of Promises?

How to Synchronize a Sequence of Promises?

Introduction

This article addresses the challenge of synchronizing a sequence of promises, ensuring that they resolve sequentially and that a rejection in one promise rejects the entire chain. This scenario presents unique implementation considerations that require a deeper understanding of promise handling.

Implementation Approaches

Using Manual Iteration

For simple cases, manual iteration can be employed, where each promise is resolved one after the other in a serial manner. This requires writing custom logic to handle the sequence and rejection gracefully.

Using Promise.reduce()

Another approach involves utilizing Promise.reduce(), which allows us to chain promises sequentially. However, it requires accumulating results in an array for subsequent processing.

Using a Modified Version of Promise.map()

For dynamic promise scenarios, a modified version of the Promise.map() method can be created to handle the sequential execution and rejection requirements.

Resolving Dynamic Promises (SOLUTION)

To meet the specific need of generating promises dynamically and ensuring sequential execution, the spex library's sequence method has been implemented. This method offers a dynamic approach to iterating through a sequence of promises, resolving them one by one, while maintaining the integrity of the sequence and the error handling logic.

The sequence Method in spex

The sequence method in spex provides a solution for sequencing promises synchronously. It takes a nextPromise function that dynamically generates the next promise in the sequence. The method iterates through the promises, resolving them sequentially, and returns a promise that resolves to the final result or rejects upon the first error encountered.

Usage Example

function sequence(nextPromise) {
  var promise = Promise.resolve();

  while (nextPromise()) {
    promise = promise.then(nextPromise);
  }

  return promise;
}

This example demonstrates how to use the sequence method to execute a dynamic sequence of promises. The nextPromise function is responsible for generating the next promise in the sequence, which is then chained to the previous promise. The sequence method ensures that the promises resolve sequentially, and it returns a promise that represents the entire sequence's completion.

The above is the detailed content of How to Synchronize a Sequence of Promises?. For more information, please follow other related articles on the PHP Chinese website!