noob-components/plugs/composables/useWatchOnce.ts

import { nextTick, Ref, watchEffect, WatchEffect } from "vue";

export function watchEffectOnce(cond: Ref<any, any>, cb: WatchEffect) {
  const stop = watchEffect((onCleanup) => {
    if (cond.value) {
      nextTick(() => stop());
      cb(onCleanup);
    }
  });

  return stop;
}