queue-callbacks

Execute callbacks in sequence.

Useful if you are accessing some shared state (eg. a database), and want to make sure that operations are performed in the right order (ie. you can read your own writes).

npm install queue-callbacks

Usage

const queue = new Queue()
queue.push(done => {
  db.put('example', 'first value', done)
})
queue.push(done => {
  db.get('example', done)
}, (err, value) => {
  console.log(value) // will print 'first value'
})
queue.push(done => {
  db.put('example', 'second value', done)
})
queue.push(done => {
  db.get('example', done)
}, (err, value) => {
  console.log(value) // will print 'second value'
})

Every job pushed to the queue will only be executed once all previous jobs have finished.

If the queue is empty, the job will be executed immediately.

A job is a function that accepts a Node-style callback as its only argument.

You can optionally pass a callback as a second argument that will be executed once the corresponding job has finished.

API

queue = new Queue()
queue.push(job: (done: Callback) => any, callback?: Callback))

// all callbacks should be Node-style callbacks.
type Callback = (err: Error, val: any) => any

Why?

There are loads of modules that do similar things, but they either do too much or have weird APIs, so I wrote this. Why not?

Contribute

PRs accepted.

License

MIT © 2018 harry lachenmayer