gen-q

^{Social Media Photo by Meizhi Lang on Unsplash}

Highliy inspired by Refillable Generators post (now 401 🤷), this module uses a modern JS approach through a class that doesn't need to provide "error prone" utilities around, as explained in my reply.

Live Demo

import Queue from 'https://esm.run/gen-q';

// forever waiting for pushes
// it exits on explicit queue reset: splice(0)
async function test(items) {
  for await (const item of items)
    console.log(item);
  console.log('done');
}

const numbers = new Queue(1, 2, 3);
test(numbers);

// it fails if it was not consumed/resetted
try {
  await test(numbers);
  console.assert(false, 'should have thrown an error');
}
catch {}

// exit the test (after 3 seconds)
setTimeout(() => {
  numbers.splice(0);
}, 3000);

setTimeout((...args) => {
  // nobody will see these items ...
  // pushed but then synchronously removed via splice
  numbers.push(...args);

  // drop all items from the queue, like map and other
  // methods it returns a new Queue itself
  console.assert(numbers.splice(0) instanceof Queue);

  // push and then loop again
  setTimeout(async () => {
    numbers.push(...args);
    await test(numbers);
    // will exit in a second
  }, 1000);
}, 1000, 4, 5, 6);

// output
// 1
// 2
// 3
// done
// 4
// 5
// 6
// done

Introducing gen-q/utils

import Queue from 'https://esm.run/gen-q';
import { forever } from 'https://esm.run/gen-q/utils';

const numbers = new Queue(1, 2, 3);

// this one will never exit + it owns the queue
(async function test(items) {
  for await (const item of forever(items))
    console.log(item);
}(numbers));

// any attempt to loop the queue will fail
// but the anonymous loop will keep going!

// exit the test (after 3 seconds)
setTimeout(() => {
  numbers.splice(0);
}, 3000);

setTimeout((...args) => {
  // nobody will see these items ...
  // pushed but then synchronously removed via splice
  numbers.push(...args);

  // drop all items from the queue, like map and other
  // methods it returns a new Queue itself
  console.assert(numbers.splice(0) instanceof Queue);

  // push at distance, the `test` is still running!
  setTimeout(async () => {
    numbers.push(...args);
  }, 1000);
}, 1000, 4, 5, 6);

// output
// 1
// 2
// 3
// 4
// 5
// 6