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React push Api response in the setState

in my EventForm i have this const, this is a dialog form
this is my EventForm.js
const EventForm = (props) => {
const { setOpenPopup, records, setRecords, setMessage, setOpenSnackbar } = props
const addEvent = () => {
axios.post('https://jsonplaceholder.typicode.com/events', (event)
.then(resp => {
console.log(resp.data)
const newData = [{
title: resp.data.name,
start: resp.data.starts_at,
end: resp.data.ends_at
}]
setRecords([{ ...records, newData}])
//
setOpenPopup(false)
setMessage('New Event added')
setOpenSnackbar(true)
})
.catch([])
}
export default EventForm
EventForm.propTypes = {
setOpenPopup: PropTypes.func,
records: PropTypes.array,
setRecords: PropTypes.func,
setMessage: PropTypes.func,
setOpenSnackbar: PropTypes.func
}
}
in my EventTable.js
const [records, setRecords] = useState([]);
useEffect(() => {
axios.get('https://jsonplaceholder.typicode.com/events')
.then(resp => {
const newData = resp.data.map((item) => ({
title: item.name,
start: item.starts_at,
end: item.ends_at
}))
setRecords(newData)
})
.catch(resp => console.log(resp))
}, [])
fullcalendar...
events={records}
im trying to push the API post response to my setRecords. so when the dialog form close it will not use the GET response. ill just get the new record and render to my view
but im getting an error:
Unhanded Rejection (TypeError): setRecords is not a function

I suspect you are using React Hooks. Make sure that your records state looks like this
const [records, setRecords] = useState([]);
In your axios request, it looks like that you are trying to spread the values of records which is an array to an object. I'd suggest refactoring this to something like this. Instead of trying to spread an array into the object, take the previous state and merge it with the new one.
setRecords(prevRecords => [...prevRecords, ...newData])
Here's an example using React Hooks how the component could look like
import React from "react";
import axios from "axios";
const MyComponent = ({
setOpenPopup,
records,
setRecords,
setMessage,
setOpenSnackbar
}) => {
const addEvent = () => {
axios
.post("https://jsonplaceholder.typicode.com/events", event) // Make sure this is defined somewhere
.then((resp) => {
const { name, starts_at, ends_at } = resp.data;
const newData = [
{
title: name,
start: starts_at,
end: ends_at
}
];
setRecords((prevRecords) => [...prevRecords, ...newData]);
setOpenPopup(false);
setMessage("New Event added");
setOpenSnackbar(true);
})
.catch([]);
};
return (
<div>
<button onClick={addEvent}>Click me </button>
</div>
);
};
export default MyComponent;
If you are not using React Hooks and use Class components, then make sure that you pass setRecords to your component in props. Plus, in your props destructuring, make sure you add this to the props, otherwise, it can lead to unwanted behaviour. Also, move your request function out of the render method and destructure values from the props that you need inside the function. I've also noticed that your axios syntax was incorrect (forgot to close after the event) so I fixed that as well. Here's an example of how you can improve it.
import React from "react";
import axios from "axios";
class MyComponent extends React.Component {
addEvent = () => {
const {
setOpenPopup,
setRecords,
setMessage,
setOpenSnackbar
} = this.props;
axios
.post("https://jsonplaceholder.typicode.com/events", event)
.then((resp) => {
console.log(resp.data);
const newData = [
{
title: resp.data.name,
start: resp.data.starts_at,
end: resp.data.ends_at
}
];
setRecords((prevRecords) => [...prevRecords, ...newData]);
//
setOpenPopup(false);
setMessage("New Event added");
setOpenSnackbar(true);
})
.catch([]);
};
render() {
return (
<div>
<button onClick={() => this.addEvent()}>Click me</button>
</div>
);
}
}
export default MyComponent;

React/Redux not rendering nextState

The common cause for my issue when researching this is mutating the state and not returning a new object of the state which causes redux to not recognize a change. However, this is not and has never been an issue and i'm well aware of it. I'm returning a new object. In the logger which you can see in the attached image it displays the successful api call resolved and the nextState is updated but never rendered. Refreshing the page acts exactly the same even though i expected to possibly need to do so upon initial landing to root page.
Component:
import pokemonReducer from '../../reducers/pokemon_reducer';
import PokemonIndexItem from './pokemon_index_item';
import {Route} from 'react-router-dom';
import PokemonDetailContainer from './pokemon_detail_container';
class PokemonIndex extends React.Component {
componentDidMount() {
this.props.requestAllPokemon();
}
render() {
const pokemon = this.props.pokemon;
return (
<section className="pokedex">
<Route path='/pokemon/:pokemonID' component={PokemonDetailContainer} />
<ul>{pokemon && pokemon.map(poke => <li>{poke.name}{poke.id}</li>)}</ul>
</section>
);
}
}
export default PokemonIndex;
and the container:
import {connect} from 'react-redux';
import { selectAllPokemon } from '../../reducers/selectors';
import PokemonIndex from './pokemon_index';
import { requestAllPokemon } from '../../actions/pokemon_actions';
const mapStateToProps = state => ({
pokemon: selectAllPokemon(state)
});
const mapDispatchToProps = dispatch => ({
requestAllPokemon: () => dispatch(requestAllPokemon())
});
export default connect(mapStateToProps, mapDispatchToProps)(PokemonIndex);
the reducer:
import { RECEIVE_ALL_POKEMON, RECEIVE_SINGLE_POKEMON} from '../actions/pokemon_actions';
const pokemonReducer = (initialState = {}, action) => {
Object.freeze(initialState);
switch(action.type) {
case RECEIVE_ALL_POKEMON:
return Object.assign({}, initialState, action.pokemon);
case RECEIVE_SINGLE_POKEMON:
let poke = action.payload.pokemon
return Object.assign({}, initialState, {[poke.id]: poke})
default:
return initialState;
}
};
export default pokemonReducer;
secondary reducer:
import { combineReducers } from 'redux';
import pokemonReducer from './pokemon_reducer'
const entitiesReducer = combineReducers({
pokemon: pokemonReducer,
});
export default entitiesReducer;
rootreducer:
import {combineReducers} from 'redux';
import entitiesReducer from './entities_reducer';
const rootReducer = combineReducers({
entities: entitiesReducer
});
export default rootReducer;
as requested here is the selectors defined in reducers folder
export const selectAllPokemon = (state) => {
Object.values(state.entities.pokemon);
};
export const selectSinglePokemon = (state) => {
Object.values(state.entities.pokemon)
};
and here is the actions created:
export const RECEIVE_ALL_POKEMON = "RECEIVE_ALL_POKEMON";
export const RECEIVE_SINGLE_POKEMON = "RECEIVE_SINGLE_POKEMON";
import * as APIUtil from '../util/api_util';
export const receiveAllPokemon = (pokemon) => (
{
type: RECEIVE_ALL_POKEMON,
pokemon
}
);
export const requestAllPokemon = () => (dispatch) => {
APIUtil.fetchAllPokemon()
.then(
pokemon =>
{ dispatch(receiveAllPokemon(pokemon));}
);
};
export const receiveSinglePokemon = data => (
{
type: RECEIVE_SINGLE_POKEMON,
data
}
);
export const requestSinglePokemon = id => (dispatch) => {
APIUtil.fetchSinglePokemon(id)
.then(pokemon => {dispatch(receiveSinglePokemon(pokemon));
return pokemon;});
};
nextstate showing in console

As you stated in your question, your redux state is getting properly set but your new state is never being rendered and I think this has to do with your selector. It looks to me that you forgot to return your computed state.
export const selectAllPokemon = (state) => {
Object.values(state.entities.pokemon);
};
// will return undefined
For returning your state you have two options:
Explicit return
export const selectAllPokemon = (state) => {
return Object.values(state.entities.pokemon);
};
Implicit return
export const selectAllPokemon = (state) => (
Object.values(state.entities.pokemon);
);
I refer to this article or look at the examples I created in playground to get a better unstanding of implicit and explicit return in arrow functions.

React: How to use one variable in one component when it is imported to another component

import React, { useEffect, useState } from 'react';
import { Card } from 'components/Card';
import { dateFilter } from 'helpers';
import Chart from 'chart.js';
import 'chartjs-chart-matrix';
import chroma from 'chroma-js';
import moment from 'moment';
const WeeklyTrafficCard = (props) => {
const { start, end, data, store } = props;
const capacity = store && store.capacity;
var numberOfweeks = 0; //representing how many weeks back
const dateArray = [];
var today = moment();
while (numberOfweeks < 10) {
var from_date = today.startOf('week').format('MM/DD/YY');
var to_date = today.endOf('week').format('MM/DD/YY');
var range = from_date.concat(' ','-',' ',to_date);
dateArray.push(range);
today = today.subtract(7, 'days');
numberOfweeks++;
//console.log(dateArray);
}
const [each_daterange, setDateRange] = useState();
I have this Component called WeeklyTrafficCard and I want to use the variable, each_daterange, in another component, which imported WeeklyTrafficCard as below to send the get request, clearly I cannot use each_daterange directly right here, how I can work around it?
import React, { useContext, useEffect, useState } from 'react';
import { WeeklyTrafficCard } from './WeeklyTrafficCard';
import { AppContext } from 'contexts/App';
import { API_URL } from 'constants/index.js';
import { todayOpen, todayClose } from 'helpers';
import moment from 'moment';
const WeeklyTrafficCardContainer = (props) => {
const { API } = useContext(AppContext);
const { store = {} } = props;
const [data, setData] = useState([]);
const open = todayOpen(store.hours, store.timezone);
const close = todayClose(store.hours, store.timezone);
useEffect(() => {
async function fetchData() {
const result = await API.get(`${API_URL}/api/aggregates`, {
params: {
each_daterange,
every: '1h',
hourStart: 13,
hourStop: 4
},
});

You should use a useEffect(prop drilling) to pass your variable in your parent:
import React, { Component } from "react";
import { render } from "react-dom";
import "./style.css";
const App = () => {
const [myVar, setMyVar] = React.useState('');
return (
<div>
<Child setMyVar={setMyVar} />
{myVar}
</div>
);
};
const Child = ({setMyVar}) => {
const myChildVar = "Hello world !"
React.useEffect( () => setMyVar(myChildVar),[]);
return <div> This is the child</div>
}
render(<App />, document.getElementById("root"));
Here is the repro on stackblitz

Understanding of the Problem
You want to pass data up to the parent from the child.
Manage each_daterange in the parent:
Instead of creating your useState variable each_daterange in the child you can declare it in the parent and pass down it's setter function. For instance:
const WeeklyTrafficCardContainer = (props) => {
const [eachDateRange, setEachDateRange] = useState();
return (
<div>
{/* your return */}
<WeeklyTrafficCard setEachDateRange={setEachDateRange} />
</div>
)
}
If you need to display eachDateRange in the traffic card, or the traffic card needs to completely own that variable, you can create another state variable in the parent and pass a callback to the child (essentially what is above but now you have two different state variables).
The parent becomes
const WeeklyTrafficCardContainer = (props) => {
const [requestDateRange, setRequestDateRange] = useState();
const updateRequestDateRange = (dateRange) => {
setRequestDateRange(dateRange)
}
return (
<div>
{/* your return */}
<WeeklyTrafficCard updateDateRange={updateRequestDateRange} />
</div>
)
}
Then in your WeeklyTrafficCard call props.updateDateRange and pass it the date range whenever each_daterange changes.

Ciao, of course you need a global state manager. My preferred is react-redux. In few word, react-redux allows you to have a state that is shared in all your components. Sharing each_daterange between WeeklyTrafficCardContainer and WeeklyTrafficCard will be very easy if you decide to use it.
This is the more appropriate guide to quick start with react-redux. have a nice coding :)

Keep the value outside of the component, where both can access it. There are other ways to do this, but just as a simple example you could create a simple "store" to hold it and reference that store from each component that needs it:
class Store {
setDateRange (newDateRange) {
this._dateRange = newDateRange;
}
get dateRange () {
return this._dateRange;
}
}
export default new Store(); // singleton; everyone gets the same instance
import store from './Store';
const WeeklyTrafficCard = (props) => {
// use current dateRange value
const dateRange = store.dateRange;
// set new dateRange
store.setDateRange( newDateRange );
// do other stuff
}
import store from './Store';
const WeeklyTrafficCardContainer = (props) => {
// use current dateRange value
const dateRange = store.dateRange;
// set new dateRange
store.setDateRange( newDateRange );
// do other stuff
}
If you want store updates to trigger component re-renders you'd need to add some higher order component plumbing, like redux's connect, or some other mechanism for triggering updates:
// pseudocode; make store an event emitter and return
// a component that re-renders on store events
store.connect = Component => {
return props => {
React.useEffect(() => {
store.addEventListener( ... )
return () => store.removeEventListener( ... )
})
}
}
Or if the components share a common parent, you could lift the state to the parent and pass the information to each component as props. If either component updates the value, the parent state change will trigger a re-render of both components with the new value:
const Parent = () => {
const [dateRange, setDateRange] = React.useState();
return (
<>
<WeeklyTrafficCardContainer
dateRange={dateRange}
onDateRangeChange={newRange => setDateRange(newRange)}
/>
<WeeklyTrafficCard
dateRange={dateRange}
onDateRangeChange={newRange => setDateRange(newRange)}
/>
</>
);
}

Let's rephrase the objective here.
Objective: access each_daterange from WeeklyTrafficCard component in WeeklyTrafficCardContainer component.
Note: simply put, choose the following case based on your problem.
choose using prop if the variable is to be accessed by only one component
choose using context if the variable is to be accessed by more than one components
Solution Cases:
Case A: using prop.
Case A.1. WeeklyTrafficCard is the parent of WeeklyTrafficCardContainer
each_datarange being passed from WeeklyTrafficCard component as prop to WeeklyTrafficCardContainer component
working example for reference: codesandbox - variable passed as prop
// WeeklyTrafficCard.jsx file
const WeeklyTrafficCard = () => {
const [each_daterange, setDateRange] = useState();
return (
<>
...
<WeeklyTrafficCardContainer eachDateRange={each_daterange} />
</>
);
};
// WeeklyTrafficCardContainer.jsx file
const WeeklyTrafficCardContainer = props => {
const eachDateRange = props.eachDateRange;
return (
<>
...
</>
);
};
Case A.2. WeeklyTrafficCard & WeeklyTrafficCardContainer are children of a parent, say WeeklyTraffic component
each_datarange will be present in WeeklyTraffic component which is shared among WeeklyTrafficCard component & WeeklyTrafficCardContainer component
// WeeklyTraffic.jsx file
const WeeklyTraffic = () => {
const [each_daterange, setDateRange] = useState();
return (
<>
...
<WeeklyTrafficCard eachDateRange={each_daterange} />
<WeeklyTrafficCardContainer eachDateRange={each_daterange} />
</>
);
};
// WeeklyTrafficCard.jsx file
const WeeklyTrafficCard = props => {
const eachDateRange = props.eachDateRange;
return (
<>
...
</>
);
};
// WeeklyTrafficCardContainer.jsx file
const WeeklyTrafficCardContainer = props => {
const eachDateRange = props.eachDateRange;
return (
<>
...
</>
);
};
Case B: using context.
follow blog example found: blog - react context
this is preferred way to implement if the variable/variables is/are shared or need to be accessed by more than 1 components

React Hooks/Context & Elastictic UI. Problem with fetched data (REST) in function Component

I'm quite new to React Hooks/Context so I'd appreciate some help. Please don' t jump on me with your sharp teeth. I Checked other solutions and some ways i've done this before but can't seem to get it here with the 'pick from the list' way.
SUMMARY
I need to get the municipios list of names inside of my const 'allMunicipios'(array of objects) inside of my Search.js and then display a card with some data from the chosen municipio.
TASK
Get the data from eltiempo-net REST API.
Use Combobox async element from Elastic UI to choose from list of municipios.
Display Card (from elastic UI too) with some info of chosen municipio.
It has to be done with function components / hooks. No classes.
I'd please appreciate any help.
WHAT I'VE DONE
I've created my reducer, context and types files in a context folder to fecth all data with those and then access data from the component.
I've created my Search.js file. Then imported Search.js in App.js.
I've accesed the REST API and now have it in my Search.js
PROBLEM
Somehow I'm not beeing able to iterate through the data i got.
Basically i need to push the municipios.NOMBRE from api to the array const allMunicipios in my search.js component. But when i console log it it gives me undefined. Can;t figure out why.
I'll share down here the relevant code/components. Thanks a lot for whoever takes the time.
municipiosReducer.js
import {
SEARCH_MUNICIPIOS,
CLEAR_MUNICIPIOS,
GET_MUNICIPIO,
GET_WEATHER,
} from "./types";
export default (state, action) => {
switch (action.type) {
case SEARCH_MUNICIPIOS:
return {
...state,
municipios: action.payload,
};
case GET_MUNICIPIO:
return {
...state,
municipio: action.payload,
};
case CLEAR_MUNICIPIOS:
return {
...state,
municipios: [],
};
case GET_WEATHER: {
return {
...state,
weather: action.payload,
};
}
default:
return state;
}
};
municipiosContext.js
import { createContext } from "react";
const municipiosContext = createContext();
export default municipiosContext;
MunicipiosState.js
import React, { createContext, useReducer, Component } from "react";
import axios from "axios";
import MunicipiosContext from "./municipiosContext";
import MunicipiosReducer from "./municipiosReducer";
import {
SEARCH_MUNICIPIOS,
CLEAR_MUNICIPIOS,
GET_MUNICIPIO,
GET_WEATHER,
} from "./types";
const MunicipiosState = (props) => {
const initialState = {
municipios: [],
municipio: {},
};
const [state, dispatch] = useReducer(MunicipiosReducer, initialState);
//Search municipios
//In arrow functions 'async' goes before the parameter.
const searchMunicipios = async () => {
const res = await axios.get(
`https://www.el-tiempo.net/api/json/v2/provincias/08/municipios`
// 08 means barcelona province. This should give me the list of all its municipios
);
dispatch({
type: SEARCH_MUNICIPIOS,
payload: res.data.municipios,
});
};
//Get Municipio
const getMunicipio = async (municipio) => {
const res = await axios.get(
`https://www.el-tiempo.net/api/json/v2/provincias/08/municipios/${municipio.CODIGOINE}`
//CODIGOINE is in this REST API kind of the ID for each municipio.
//I intent to use this later to get the weather conditions from each municipio.
);
dispatch({ type: GET_MUNICIPIO, payload: res.municipio });
};
const dataMunicipiosArray = [searchMunicipios];
//Clear Municipios
const clearMunicipios = () => {
dispatch({ type: CLEAR_MUNICIPIOS });
};
return (
<MunicipiosContext.Provider
value={{
municipios: state.municipios,
municipio: state.municipio,
searchMunicipios,
getMunicipio,
clearMunicipios,
dataMunicipiosArray,
}}
>
{props.children}
</MunicipiosContext.Provider>
);
};
export default MunicipiosState;
Search.js
import "#elastic/eui/dist/eui_theme_light.css";
import "#babel/polyfill";
import MunicipiosContext from "../contexts/municipiosContext";
import MunicipiosState from "../contexts/MunicipiosState";
import { EuiComboBox, EuiText } from "#elastic/eui";
import React, { useState, useEffect, useCallback, useContext } from "react";
const Search = () => {
const municipiosContext = useContext(MunicipiosContext);
const { searchMunicipios, municipios } = MunicipiosState;
useEffect(() => {
return municipiosContext.searchMunicipios();
}, []);
const municipiosFromContext = municipiosContext.municipios;
const bringOneMunicipio = municipiosContext.municipios[0];
let municipiosNames = municipiosFromContext.map((municipio) => {
return { label: `${municipio.NOMBRE}` };
});
console.log(`municipiosFromContext`, municipiosFromContext);
console.log(`const bringOneMunicipio:`, bringOneMunicipio);
console.log(`municipiosNames:`, municipiosNames);
const allMunicipios = [
{ label: "santcugat" },
{ label: "BARCELONETA" },
{ label: "BARCE" },
];
const [selectedOptions, setSelected] = useState([]);
const [isLoading, setLoading] = useState(false);
const [options, setOptions] = useState([]);
let searchTimeout;
const onChange = (selectedOptions) => {
setSelected(selectedOptions);
};
// combo-box
const onSearchChange = useCallback((searchValue) => {
setLoading(true);
setOptions([]);
clearTimeout(searchTimeout);
// eslint-disable-next-line react-hooks/exhaustive-deps
searchTimeout = setTimeout(() => {
// Simulate a remotely-executed search.
setLoading(false);
setOptions(
municipiosNames.filter((option) =>
option.label.toLowerCase().includes(searchValue.toLowerCase())
)
);
}, 1200);
}, []);
useEffect(() => {
// Simulate initial load.
onSearchChange("");
}, [onSearchChange]);
return (
<div>
<EuiComboBox
placeholder="Search asynchronously"
async
options={options}
selectedOptions={selectedOptions}
isLoading={isLoading}
onChange={onChange}
onSearchChange={onSearchChange}
/>
<button>Lista de municipios</button>
</div>
);
};
export default Search;
also the
Home.js
import React, { useState } from "react";
import { EuiComboBox, EuiText } from "#elastic/eui";
// import { DisplayToggles } from "../form_controls/display_toggles";
import "#babel/polyfill";
import "#elastic/eui/dist/eui_theme_light.css";
import Search from "./Search";
import MunicipioCard from "./MunicipioCard";
const Home = () => {
return (
<div>
<EuiText grow={false}>
<h1>Clima en la provincia de Barcelona</h1>
<h2>Por favor seleccione un municipio</h2>
</EuiText>
<Search />
<MunicipioCard />
</div>
);
};
export default Home;
App.js
import "#babel/polyfill";
import "#elastic/eui/dist/eui_theme_light.css";
import { EuiText } from "#elastic/eui";
import React from "react";
import Home from "./components/Home";
import MunicipiosState from "./contexts/MunicipiosState";
import "./App.css";
function App() {
return (
<MunicipiosState>
<div className="App">
<EuiText>
<h1>App Component h1</h1>
</EuiText>
<Home />
</div>
</MunicipiosState>
);
}
export default App;

You are using forEach and assigning the returned value to a variable, however forEach doesn't return anything. You should instead use map
let municipiosNames = municipiosFromContext.map((municipio) => {
return `label: ${municipio.NOMBRE}`;
});
As per your comment:
you data is loaded asynchronously, so it won't be available on first render and since functional components depend on closures, you onSearchChange function takes the value from the closure at the time of creation and even if you have a setTimeout within it the updated value won't reflect
The solution here is to add municipiosFromContext as a dependency to useEffect
const onSearchChange = useCallback((searchValue) => {
setLoading(true);
setOptions([]);
clearTimeout(searchTimeout);
// eslint-disable-next-line react-hooks/exhaustive-deps
searchTimeout = setTimeout(() => {
// Simulate a remotely-executed search.
setLoading(false);
setOptions(
municipiosNames.filter((option) =>
option.label.toLowerCase().includes(searchValue.toLowerCase())
)
);
}, 1200);
}, [municipiosFromContext]);
useEffect(() => {
// Simulate initial load.
onSearchChange("");
}, [onSearchChange]);

React Context API and avoiding re-renders

I have updated this with an update at the bottom
Is there a way to maintain a monolithic root state (like Redux) with multiple Context API Consumers working on their own part of their Provider value without triggering a re-render on every isolated change?
Having already read through this related question and tried some variations to test out some of the insights provided there, I am still confused about how to avoid re-renders.
Complete code is below and online here: https://codesandbox.io/s/504qzw02nl
The issue is that according to devtools, every component sees an "update" (a re-render), even though SectionB is the only component that sees any render changes and even though b is the only part of the state tree that changes. I've tried this with functional components and with PureComponent and see the same render thrashing.
Because nothing is being passed as props (at the component level) I can't see how to detect or prevent this. In this case, I am passing the entire app state into the provider, but I've also tried passing in fragments of the state tree and see the same problem. Clearly, I am doing something very wrong.
import React, { Component, createContext } from 'react';
const defaultState = {
a: { x: 1, y: 2, z: 3 },
b: { x: 4, y: 5, z: 6 },
incrementBX: () => { }
};
let Context = createContext(defaultState);
class App extends Component {
constructor(...args) {
super(...args);
this.state = {
...defaultState,
incrementBX: this.incrementBX.bind(this)
}
}
incrementBX() {
let { b } = this.state;
let newB = { ...b, x: b.x + 1 };
this.setState({ b: newB });
}
render() {
return (
<Context.Provider value={this.state}>
<SectionA />
<SectionB />
<SectionC />
</Context.Provider>
);
}
}
export default App;
class SectionA extends Component {
render() {
return (<Context.Consumer>{
({ a }) => <div>{a.x}</div>
}</Context.Consumer>);
}
}
class SectionB extends Component {
render() {
return (<Context.Consumer>{
({ b }) => <div>{b.x}</div>
}</Context.Consumer>);
}
}
class SectionC extends Component {
render() {
return (<Context.Consumer>{
({ incrementBX }) => <button onClick={incrementBX}>Increment a x</button>
}</Context.Consumer>);
}
}
Edit: I understand that there may be a bug in the way react-devtools detects or displays re-renders. I've expanded on my code above in a way that displays the problem. I now cannot tell if what I am doing is actually causing re-renders or not. Based on what I've read from Dan Abramov, I think I'm using Provider and Consumer correctly, but I cannot definitively tell if that's true. I welcome any insights.

There are some ways to avoid re-renders, also make your state management "redux-like". I will show you how I've been doing, it far from being a redux, because redux offer so many functionalities that aren't so trivial to implement, like the ability to dispatch actions to any reducer from any actions or the combineReducers and so many others.
Create your reducer
export const initialState = {
...
};
export const reducer = (state, action) => {
...
};
Create your ContextProvider component
export const AppContext = React.createContext({someDefaultValue})
export function ContextProvider(props) {
const [state, dispatch] = useReducer(reducer, initialState)
const context = {
someValue: state.someValue,
someOtherValue: state.someOtherValue,
setSomeValue: input => dispatch('something'),
}
return (
<AppContext.Provider value={context}>
{props.children}
</AppContext.Provider>
);
}
Use your ContextProvider at top level of your App, or where you want it
function App(props) {
...
return(
<AppContext>
...
</AppContext>
)
}
Write components as pure functional component
This way they will only re-render when those specific dependencies update with new values
const MyComponent = React.memo(({
somePropFromContext,
setSomePropFromContext,
otherPropFromContext,
someRegularPropNotFromContext,
}) => {
... // regular component logic
return(
... // regular component return
)
});
Have a function to select props from context (like redux map...)
function select(){
const { someValue, otherValue, setSomeValue } = useContext(AppContext);
return {
somePropFromContext: someValue,
setSomePropFromContext: setSomeValue,
otherPropFromContext: otherValue,
}
}
Write a connectToContext HOC
function connectToContext(WrappedComponent, select){
return function(props){
const selectors = select();
return <WrappedComponent {...selectors} {...props}/>
}
}
Put it all together
import connectToContext from ...
import AppContext from ...
const MyComponent = React.memo(...
...
)
function select(){
...
}
export default connectToContext(MyComponent, select)
Usage
<MyComponent someRegularPropNotFromContext={something} />
//inside MyComponent:
...
<button onClick={input => setSomeValueFromContext(input)}>...
...
Demo that I did on other StackOverflow question
Demo on codesandbox
The re-render avoided
MyComponent will re-render only if the specifics props from context updates with a new value, else it will stay there.
The code inside select will run every time any value from context updates, but it does nothing and is cheap.
Other solutions
I suggest check this out Preventing rerenders with React.memo and useContext hook.

I made a proof of concept on how to benefit from React.Context, but avoid re-rendering children that consume the context object. The solution makes use of React.useRef and CustomEvent. Whenever you change count or lang, only the component consuming the specific proprety gets updated.
Check it out below, or try the CodeSandbox
index.tsx
import * as React from 'react'
import {render} from 'react-dom'
import {CountProvider, useDispatch, useState} from './count-context'
function useConsume(prop: 'lang' | 'count') {
const contextState = useState()
const [state, setState] = React.useState(contextState[prop])
const listener = (e: CustomEvent) => {
if (e.detail && prop in e.detail) {
setState(e.detail[prop])
}
}
React.useEffect(() => {
document.addEventListener('update', listener)
return () => {
document.removeEventListener('update', listener)
}
}, [state])
return state
}
function CountDisplay() {
const count = useConsume('count')
console.log('CountDisplay()', count)
return (
<div>
{`The current count is ${count}`}
<br />
</div>
)
}
function LangDisplay() {
const lang = useConsume('lang')
console.log('LangDisplay()', lang)
return <div>{`The lang count is ${lang}`}</div>
}
function Counter() {
const dispatch = useDispatch()
return (
<button onClick={() => dispatch({type: 'increment'})}>
Increment count
</button>
)
}
function ChangeLang() {
const dispatch = useDispatch()
return <button onClick={() => dispatch({type: 'switch'})}>Switch</button>
}
function App() {
return (
<CountProvider>
<CountDisplay />
<LangDisplay />
<Counter />
<ChangeLang />
</CountProvider>
)
}
const rootElement = document.getElementById('root')
render(<App />, rootElement)
count-context.tsx
import * as React from 'react'
type Action = {type: 'increment'} | {type: 'decrement'} | {type: 'switch'}
type Dispatch = (action: Action) => void
type State = {count: number; lang: string}
type CountProviderProps = {children: React.ReactNode}
const CountStateContext = React.createContext<State | undefined>(undefined)
const CountDispatchContext = React.createContext<Dispatch | undefined>(
undefined,
)
function countReducer(state: State, action: Action) {
switch (action.type) {
case 'increment': {
return {...state, count: state.count + 1}
}
case 'switch': {
return {...state, lang: state.lang === 'en' ? 'ro' : 'en'}
}
default: {
throw new Error(`Unhandled action type: ${action.type}`)
}
}
}
function CountProvider({children}: CountProviderProps) {
const [state, dispatch] = React.useReducer(countReducer, {
count: 0,
lang: 'en',
})
const stateRef = React.useRef(state)
React.useEffect(() => {
const customEvent = new CustomEvent('update', {
detail: {count: state.count},
})
document.dispatchEvent(customEvent)
}, [state.count])
React.useEffect(() => {
const customEvent = new CustomEvent('update', {
detail: {lang: state.lang},
})
document.dispatchEvent(customEvent)
}, [state.lang])
return (
<CountStateContext.Provider value={stateRef.current}>
<CountDispatchContext.Provider value={dispatch}>
{children}
</CountDispatchContext.Provider>
</CountStateContext.Provider>
)
}
function useState() {
const context = React.useContext(CountStateContext)
if (context === undefined) {
throw new Error('useCount must be used within a CountProvider')
}
return context
}
function useDispatch() {
const context = React.useContext(CountDispatchContext)
if (context === undefined) {
throw new Error('useDispatch must be used within a AccountProvider')
}
return context
}
export {CountProvider, useState, useDispatch}

To my understanding, the context API is not meant to avoid re-render but is more like Redux. If you wish to avoid re-render, perhaps looks into PureComponent or lifecycle hook shouldComponentUpdate.
Here is a great link to improve performance, you can apply the same to the context API too