queue.md

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Queue

Simply import the module and start using it as follows:

import { ExpirableQueue } from 'expirables';
const queue = new ExpirableQueue();
queue.enqueue('value');
queue.dequeue();

You can also pass a second parameter to the enqueue method to override the default expiration time (0) for that entry:

queue.enqueue('value', 2000); // 2000 is the expiration time in milliseconds for this entry

The ExpirableQueue also has a setExpiration method which takes a Symbol (Returned from the enqueue method) and a timeInMs arguments and expires the entry associated with that index after the specified expiration time:

const key = queue.enqueue('value');
queue.setExpiration(key, 2000); // Expires the entry associated with the index 0 after 2000 milliseconds

How does this work?

The ExpirableQueue constructor can take two arguments:

• options (Object, if only partially specified, the rest will be set to their default values): An object containing the following properties:
  • defaultTtl (Number): The default expiration time in milliseconds for the entries in the queue. Defaults to 0 (never expires).
  • unrefTimeouts (Boolean): Whether or not to unref the timeout. Defaults to false. Here's an explanation of what this means and why it matters you.
• entries (Array): An array of entries to initialize the queue with. Each entry can be either a value or an array containing the value and the expiration time in milliseconds (Default: defaultTtl)

Hooks

The ExpirableQueue class has hooks that you can use to execute some code in certain points of the queue's lifecycle.

Available Hooks

The ExpirableQueue class has the following hooks:

• beforeExpire (Function): A function that will be called before an entry is expired. It takes the following arguments:
  • value (Any): The value of the entry that is about to be expired.
  • key (Symbol): The key of the entry that is about to be expired.
• afterExpire (Function): A function that will be called after an entry is expired. It takes the following arguments:
  • value (Any): The value of the entry that was expired.
  • key (Symbol): The key of the entry that was expired.

How to use them?

You can use the hooks by calling the addHook method on the ExpirableQueue instance:

const queue = new ExpirableQueue();
queue.addHook('beforeExpire', (value) => {
  console.log(`The value ${value} is about to expire`);
});
queue.addHook('afterExpire', (value) => {
  console.log(`The value ${value} has expired`);
});

this keyword

The this keyword in the hooks will refer to the ExpirableQueue instance.

What if I put the same value multiple times?

The ExpirableQueue doesn't consider value uniqueness. If you put the same value multiple times, it will be considered as different entries and will be expired independently. If you want to have a unique value in the queue, please consider using the ExpirableSet instead.