Update state that depends on other calculated state in React-Hooks - reactjs

Question

I want to update a state (data) that depends on other calculated state (server)
setServer(prevTweets =>
[...json, ...prevTweets].filter(
(e, i, arr) => i === arr.findIndex(t => t.tweetId === e.tweetId)
)
)
The data above will be used to set the state below (data) :
let totalPositive = 0;
let totalNegative = 0;
let totalNeutral = 0;
server.forEach(tweet => {
if(tweet.sentiment >0) totalPositive++;
if(tweet.sentiment < 0) totalNegative++;
if(tweet.sentiment ===0) totalNeutral++;
})
setData([
{ name: 'Positive', value: totalPositive },
{ name: 'Negative', value: totalNegative },
{ name: 'Neutral', value: totalNeutral },
])
Since it's asynchronous, the setData operation is always late. I know that I can use useEffect but apparently it will make an infinite loop and it's not right to use it in this case.

Answer 1

If you set the new data before you set the server you'd skip one render:
//still defaults to server so if you do't pass anything it;s still the same
const setNewData = (newServer = server) => {
const [
totalPositive,
totalNegative,
totalNeutral,
] = newServer.reduce(
([pos, neg, neu], { sentiment }) =>
sentiment > 0
? [pos + 1, neg, neu]
: sentiment < 0
? [pos, neg + 1, neu]
: [pos, neg, neu + 1],
[0, 0, 0]
);
setData([
{ name: 'Positive', value: totalPositive },
{ name: 'Negative', value: totalNegative },
{ name: 'Neutral', value: totalNeutral },
]);
};
setServer(prevTweets => {
const newServer = uniqueByTweetId([
...json,
...prevTweets,
]);
setNewData(newServer);
return newServer;
});
Unrelated to the question but could be important is that the way you get unique values could be improved. You could get unique values in one pass without having to call find index many times:
const uniqueBy = getter => arr => {
const items = new Map();
return arr.filter(item => {
const key = getter(item);
const ret = items.get(key);
items.set(key,true);
return !ret;
});
};
const data = [
{ id: 1 },
{ id: 2 },
{ id: 3 },
{ id: 4 },
{ id: 5 },
{ id: 1 },
{ id: 7 },
{ id: 1 },
{ id: 7 },
{ id: 8 },
{ id: 1 },
];
const uniqueById = uniqueBy(i => i.id);
console.log(uniqueById(data));