dezalgo

What is dezalgo?

The dezalgo npm package ensures that a callback is always called asynchronously, and not in the same tick of the event loop that it was added in, even if it is already complete. This is useful for preventing stack overflows and ensuring consistent asynchronous behavior.

What are dezalgo's main functionalities?

Ensuring asynchronous callback execution

This feature wraps a callback function to ensure that it is always called on the next tick of the event loop, even if it could be called immediately.

const dezalgo = require('dezalgo')
const callback = dezalgo((err, data) => {
  // This will always run asynchronously
  console.log('Callback called asynchronously')
})

// Even if we call it synchronously, it will be deferred
callback(null, 'some data')

Other packages similar to dezalgo

process-nextick-args

This package is similar to dezalgo in that it defers the execution of callbacks to the next tick of the event loop. It also allows for passing arguments to the callback, similar to how 'Function.prototype.apply' works.

setimmediate

The setimmediate package provides a way to execute a function asynchronously as soon as possible, but after the current event loop tick. It is similar to dezalgo but uses a different mechanism (setImmediate) which is a standard part of the Node.js and browser environments.

async

The async package offers a wide range of functions for working with asynchronous code. One of its utilities, 'async.nextTick', is similar to dezalgo in that it ensures a callback is called on the next tick of the event loop.

README

dezalgo

Contain async insanity so that the dark pony lord doesn't eat souls

See this blog post.

USAGE

Pass a callback to dezalgo and it will ensure that it is always called in a future tick, and never in this tick.

var dz = require('dezalgo')

var cache = {}
function maybeSync(arg, cb) {
  cb = dz(cb)

  // this will actually defer to nextTick
  if (cache[arg]) cb(null, cache[arg])

  fs.readFile(arg, function (er, data) {
    // since this is *already* defered, it will call immediately
    if (er) cb(er)
    cb(null, cache[arg] = data)
  })
}