Currently we can pass an array as second argument when using useCallback or useEffect like below:

useCallback(()=> {
  doSth(a, b)
}, [a, b]) // how to do deep equal if a is an object ?

The problem is it only compare array items with ===, it there any way to compare complex object ?

Support custom comparator as third argument looks not bad:

useCallback(()=> {
  doSth(a, b)
  }, 
  [complexObject], 
  (item, previousItem)=> { //custom compare logic, return true || false here }
)