weak-target

A base class to weakly target any reference.

Inspired by this post so that the example code would be instead:

import WeakTarget from 'weak-target';

class Counter extends WeakTarget {
  constructor(target) {
    super(target);
    this.timer = 0;
    this.count = 0;
    this.start();
  }

  // if present, invoked when `target` is garbage collected
  destructor() {
    console.log('Garabage Collector ran and element is GONE – clean up interval');
    this.stop();
  }

  start() {
    if (this.timer) return;
    this.count = 0;
    const tick = () => {
      const { target } = this;
      // always check if the target exists because WeakRef could be freed
      // before the FinalizationRegistry callback gets a chance to run
      if (target) {
        console.log('Element is still in memory, updating count.');
        target.textContent = `Counter: ${++this.count}`;
      }
    };
    tick();
    this.timer = setInterval(tick, 1000);
  }

  stop() {
    if (this.timer) {
      clearInterval(this.timer);
      this.timer = 0;
    }
  }
}

Live Demo

That's it, the class orchestrate with ease the ability to retrieve a target reference that might has gone.

If there is a destructor method attached, this will get invoked whenever that happens, either by accessing target explicitly, in case the FinalizationRegistry hasn't called the callback yet, or implicitly, when such callback gets executed.

The destructor is not meant to be invoked directly and it will be invoked only once, like it is for the constructor.