Orderly Queue

Implementation of a promise-based FIFO queuing system using ES2017 async generators.

npm:npm i orderly-queue -S
Babel:babel-plugin-syntax-async-generators

• Takes a function that returns a promise (or Promise.all)
• Invokes the promise and yields the eventual result
• Awaits the completion of the task before beginning the next
• Implements a pseudo-observable for next and error
• Passes the returned props along to the next task

Usage

importQueuefrom'orderly-queue';constqueue=Queue({value: ['Blueberries'],next: console.log});queue.process(fruits=>Promise.resolve([...fruits,'Apples']));queue.process(fruits=>Promise.resolve([...fruits,'Bananas']));queue.process(fruits=>Promise.resolve([...fruits,'Raspberries']));// > ['Blueberries']// > ['Blueberries', 'Apples']// > ['Blueberries', 'Apples', 'Bananas']// > ['Blueberries', 'Apples', 'Bananas', 'Raspberries']

Each task will wait before the completion of the current task, meaning you can safely assume the order of fruits no matter how long it takes for a single task to complete.

Errors

Any errors that are raised will be passed to the error function, however the items in the queue will continue to be invoked one-at-a-time passing in the props from the last successful invocation.

importQueuefrom'orderly-queue';constqueue=Queue({value: ['Blueberries'],next: console.log,error: console.log});queue.process(fruits=>Promise.resolve([...fruits,'Apples']));queue.process(fruits=>Promise.reject('Error: Fruitless...'));queue.process(fruits=>Promise.resolve([...fruits,'Bananas']));queue.process(fruits=>Promise.resolve([...fruits,'Raspberries']));// > ['Blueberries']// > ['Blueberries', 'Apples']// > Error: Fruitless...// > ['Blueberries', 'Apples', 'Bananas']// > ['Blueberries', 'Apples', 'Bananas', 'Raspberries']

In cases where you wish to end the iterator early you can invoke the abort method — perhaps in response to an error being raised. Any queued tasks will not be run.

constqueue=Queue({value: ['Blueberries'],next: console.log,error: console.log});// ...queue.abort();