React hooks useState setValue still rerender one more time when value is equal
This thread may help you : React: Re-Rendering on Setting State - Hooks vs. this.setState
Also, you can check the second paragraph over here which says:
Note that React may still need to render that specific component again before bailing out. That shouldn’t be a concern because React won’t unnecessarily go “deeper” into the tree. If you’re doing expensive calculations while rendering, you can optimize them with useMemo.
React can’t guess the ouput of render() won’t change: it has to render() again and compare the results with the previous render().
Then the magic happens: if there are no differences, the DOM is not updated; if there are differences, it tries to only create/destroy elements as needed, because that’s the expensive part, not running render() — well it should not be.
Changing the state normally triggers a call to render() (not necessarily DOM modifications) — but if you want control over that behavior, define
Note: That goes for non-hook components. However, I didn’t know the behavior of hooks was slightly different from that of a regular component: it seems that you’re right in expecting
setState not to trigger a render when the value is unchanged — see Yash Joshi's answer.