Можем ли мы зациклить watch? Как от этого предостеречься?

Yes, a watch (observer) can enter a loop if, when data changes, an event occurs that triggers another change, and so on — resulting in an infinite update cycle.

To avoid this:

• Use conditional checks inside the watch to respond only to significant changes.
• Avoid directly modifying observed data within the watch itself without additional logic.
• In some frameworks, you can use the immediate: false option or similar to prevent the watch from running on initialization.
• If you need to update data from the watch, do it asynchronously or with a delay to prevent recursion.

Example in Vue.js:

watch(() => someData.value, (newVal, oldVal) => {
  if (newVal !== oldVal && !updating) {
    updating = true;
    // update data
    someOtherData.value = compute(newVal);
    updating = false;
  }
});

Here, the updating flag prevents the watch from re-triggering due to changes within it.