inflight

What is inflight?

The inflight npm package is used to manage and track the state of asynchronous operations to ensure that the same operation isn't initiated multiple times before it completes. It's particularly useful when dealing with file system operations or any other tasks that should not be duplicated.

What are inflight's main functionalities?

Tracking inflight operations

This code sample demonstrates how to use the inflight package to prevent the same asynchronous operation from being executed multiple times simultaneously. It uses a timeout to simulate an asynchronous operation and ensures that if the operation is already in progress, subsequent calls will not initiate a new one.

const inflight = require('inflight');

function asyncOperation(key, callback) {
  if (inflight(key)) return;
  inflight(key, callback);
  // Perform the operation here
  setTimeout(() => {
    // Operation completed
    inflight(key, null);
    callback();
  }, 1000);
}

asyncOperation('operation1', () => console.log('Operation 1 completed.'));
asyncOperation('operation1', () => console.log('Operation 1 is already in flight.'));

Other packages similar to inflight

async

The async package provides a collection of utilities to work with asynchronous JavaScript. While it doesn't offer the exact same functionality as inflight, it does include methods like 'async.queue' and 'async.cargo' which can be used to manage concurrency and ensure that certain tasks are not overlapped.

p-limit

p-limit is a package that limits the number of promises that are running at any one time. It can be used to control concurrency similar to inflight, but it works specifically with promises rather than general asynchronous operations.

once

The once package ensures a function can only be called once. It's similar to inflight in that it prevents duplicate execution, but it's more general-purpose and not specifically designed for tracking the state of asynchronous operations.

README

inflight

Add callbacks to requests in flight to avoid async duplication

USAGE

var inflight = require('inflight')

// some request that does some stuff
function req(key, callback) {
  // key is any random string.  like a url or filename or whatever.
  //
  // will return either a falsey value, indicating that the
  // request for this key is already in flight, or a new callback
  // which when called will call all callbacks passed to inflightk
  // with the same key
  callback = inflight(key, callback)

  // If we got a falsey value back, then there's already a req going
  if (!callback) return

  // this is where you'd fetch the url or whatever
  // callback is also once()-ified, so it can safely be assigned
  // to multiple events etc.  First call wins.
  setTimeout(function() {
    callback(null, key)
  }, 100)
}

// only assigns a single setTimeout
// when it dings, all cbs get called
req('foo', cb1)
req('foo', cb2)
req('foo', cb3)
req('foo', cb4)