React use [shallow comparision](https://learntechsystems.com/what-is-shallow-comparison-in-js/) (values are equals in case of primitive types. In case of object it just check the reference) to check if the dependency changes between renders, this can conduce to bugs in the following situa

### Always use a depency array

```js
useEffect(() => {
  setCount((count) => count + 1);
}, []);
```

### Function as dependency

React re defines functions on every render, so the dependency always changes, use `useCallback` to memoize the function so it doesn't change

```js
const logResult = useCallback(() => {
  return 2 + 2;
}, []);

useEffect(()=> {
  setCount((count) => count + 1);
}, [logResult]);
```

### Array as dependency

The reference to an array changes in every render, use `useRef` so it doesn't change

```js
const [count, setCount] = useState(0);
//extract the 'current' property and assign it a value
const { current: myArray } = useRef(["one", "two", "three"]);

useEffect(() => {
  setCount((count) => count + 1);
}, [myArray]);
```
### Object as dependency

The reference to an object changes in every render, use `useMemo` so it doesn't change

```js
const person = useMemo(
  () => ({ name: "Rue", age: 17 }),
  [] //no dependencies so the value doesn't change
);
useEffect(() => {
  setCount((count) => count + 1);
}, [person]);
```

[source](https://blog.logrocket.com/solve-react-useeffect-hook-infinite-loop-patterns/)
