p-scheduler

p-scheduler providing a controlled way to manage the execution order of promises. It leverages proxies to queue and manage promises, making it easier to handle asynchronous operations sequentially, especially asynchronous third-party dependencies.

Installation

npm install p-scheduler

Usage

Importing and Initializing

First, import the p-scheduler class and create an instance of it. You can pass an optional boolean parameter to the constructor to enable or disable automatic promise resolution.

import PScheduler from 'p-scheduler';

const scheduler = new PScheduler(); // Auto mode enabled by default
const manualScheduler = new PScheduler(false); // Auto mode disabled

Adding Asynchronous Functions

To add a function to the scheduler, use the add method. This method returns a proxied version of the function that will be executed according to the scheduler's rules.

const proxiedFunction = scheduler.add(originalFunction);

Auto Mode

In auto mode, promises are resolved automatically in the order they were added. This is the default behavior.

const scheduler = new PScheduler();

const fn1 = scheduler.add(async () => {
  console.log('Function 1');
});

const fn2 = scheduler.add(async () => {
  console.log('Function 2');
});

fn1();
fn2();

In this example, "Function 1" will always be logged before "Function 2", regardless of the individual execution times of the functions.

Manual Mode

In manual mode, you have control over when the next promise in the queue is resolved by calling the next or nextAll methods.

const scheduler = new PScheduler(false);

const fn1 = scheduler.add(async () => {
  console.log('Function 1');
});

const fn2 = scheduler.add(async () => {
  console.log('Function 2');
});

fn1();
fn2();

// Manually resolve the next promise in the queue
scheduler.next(); // Logs: "Function 1"

// Resolve all remaining promises in the queue
scheduler.nextAll(); // Logs: "Function 2"

API

Constructor

constructor(auto?: boolean)

• auto (optional): A boolean indicating whether promises should be resolved automatically. Defaults to true.

Methods

add

add(fn: Function): Function

• fn: The function to be added to the scheduler.
• Returns: A proxied version of the function.

next

next(): void

Resolves the next promise in the queue. Only available when auto is set to false.

nextAll

nextAll(): void

Resolves all remaining promises in the queue. Only available when auto is set to false.

Example

Here is a complete example demonstrating the usage of p-scheduler:

import PScheduler from 'p-scheduler';

const scheduler = new PScheduler();

const fn1 = scheduler.add(async () => {
  console.log('Function 1');
  return 'Result 1';
});

const fn2 = scheduler.add(async () => {
  console.log('Function 2');
  return 'Result 2';
});

fn1().then(result => console.log(result));
fn2().then(result => console.log(result));

Output:

Function 1
Result 1
Function 2
Result 2

In this example, "Function 1" and its result will always be logged before "Function 2" and its result, maintaining the order of execution.

Credits

Inspired by p-mutex