after

What is after?

The 'after' npm package is a small utility that helps manage asynchronous operations by executing a callback after a specified number of operations have completed. It is particularly useful for scenarios where you need to wait for multiple asynchronous tasks to finish before proceeding.

What are after's main functionalities?

Execute callback after multiple asynchronous operations

This feature allows you to specify a callback function that will be executed after a certain number of asynchronous operations have completed. In this example, the callback will be executed after three tasks have finished.

const after = require('after');

const done = after(3, () => {
  console.log('All tasks completed');
});

setTimeout(() => {
  console.log('Task 1 done');
  done();
}, 1000);

setTimeout(() => {
  console.log('Task 2 done');
  done();
}, 2000);

setTimeout(() => {
  console.log('Task 3 done');
  done();
}, 3000);

Other packages similar to after

async

The 'async' package provides a wide range of utilities for working with asynchronous JavaScript, including functions for parallel and series execution, queue management, and more. It is more feature-rich compared to 'after' and can handle more complex asynchronous workflows.

promise

The 'promise' package is a lightweight implementation of Promises/A+ that allows you to work with asynchronous operations in a more modern and flexible way compared to callbacks. It provides methods like 'all' and 'race' to manage multiple promises, making it a more versatile option than 'after'.

bluebird

The 'bluebird' package is a fully-featured Promise library that offers advanced features like cancellation, iteration methods, and more. It is more powerful and flexible than 'after', making it suitable for complex asynchronous workflows.

README

After

Invoke callback after n calls

Status: production ready

Example

var after = require("after")
var db = require("./db") // some db.

var updateUser = function (req, res) {
  // use after to run two tasks in parallel,
  // namely get request body and get session
  // then run updateUser with the results
  var next = after(2, updateUser)
  var results = {}
  
  getJSONBody(req, res, function (err, body) {
    if (err) return next(err)
    
    results.body = body
    next(null, results)
  })
  
  getSessionUser(req, res, function (err, user) {
    if (err) return next(err)
    
    results.user = user
    next(null, results)
  })
  
  // now do the thing!
  function updateUser(err, result) {
    if (err) {
      res.statusCode = 500
      return res.end("Unexpected Error")
    }
    
    if (!result.user || result.user.role !== "admin") {
      res.statusCode = 403
      return res.end("Permission Denied")
    }
    
    db.put("users:" + req.params.userId, result.body, function (err) {
      if (err) {
        res.statusCode = 500
        return res.end("Unexpected Error")
      }
      
      res.statusCode = 200
      res.end("Ok")  
    })   
  }
}

Naive Example

var after = require("after")
    , next = after(3, logItWorks)

next()
next()
next() // it works

function logItWorks() {
    console.log("it works!")
}

Example with error handling

var after = require("after")
    , next = after(3, logError)

next()
next(new Error("oops")) // logs oops
next() // does nothing

// This callback is only called once.
// If there is an error the callback gets called immediately
// this avoids the situation where errors get lost.
function logError(err) {
    console.log(err)
}

Installation

npm install after

Tests

npm test

Contributors

• Raynos
• defunctzombie

MIT Licenced