proposal improvement: detach listener and attach

[betula]

listen: (ev, fn) => (
    ev[0].indexOf(fn) < 0 && (ev[0] = ev[0].concat(fn)),
    () => {
      let i = ev[0].indexOf(fn)
      i > -1 && ev[0].splice(i, 1) // error here with iteration exactly all listeners in "ev" function
    }
  )

Reason:

• If I detach another listener in the body of one listener, another listener should never be called.
• If I attach the new listener in the body of one listener, the new listener should be called only on the next reaction.

[betula]

The example above has an error. If I at first add a new listener, and at second remove the old one.

module.exports = {
  event: () => {
    let ev = (data) => {
      ev[1] ++;
      try {
          for (ev[3] = 0; i < ev[0].length; ev[3]++)
            ev[0][ev[3]](data)
      }
      finally {
          ev[1]--;
          if (!ev[1] && ev[2].length) {
            ev[0] = ev[0].concat(ev[2]);
            ev[2].length = 0;
          }
      }
    }
    ev[0] = []
    ev[1] = 0 // listen phase
    ev[2] = [] // new listeners
    ev[3] = 0 // current iteration index
    return ev
  },
  listen: (ev, fn) => (
    ev[0].indexOf(fn) < 0 && (ev[1] ? (ev[2].indexOf(fn) < 0 && ev[2].push(fn)) : ev[0].push(fn)),
    () => {
      let i = ev[0].indexOf(fn)
      i > -1 && (ev[1] && i <= ev[3] && ev[3]--, ev[0].splice(i, 1))
      i = ev[2].indexOf(fn)
      i > -1 && ev[2].splice(i, 1)
    }
  )
}

I should check its performance. Compare it with the original algorithm. We should understand how much we will miss.

[betula]

50% - 100% slower

evemin/perf_algo_test.js

Lines 6 to 17 in 6c9f985

	➜ evemin git:(main) ✗ node perf_algo_test.js
	origin
	87.53 105.24 106.76 105.22 104.91 103.82 104.55 104.74 104.72 104.75
	modified
	158.49 159.25 157.6 156.54 157.11 156.58 156.76 157.47 156.16 157.14
	600000000
	➜ evemin git:(main) ✗ bun run perf_algo_test.js
	origin
	56.84 52.23 69.22 52.34 50.9 52.03 51.47 52.82 51.62 52.58
	modified
	98.65 123.16 97.3 97.64 98.09 98.2 99.02 98.56 98.6 97.76
	600000000