I am making a simple react application in which I am in the need to display user list in select dropdown.
This user list comes from api.
So I am using Context API in my application and I have made a context and made the api call inside the context.
context.js
import React from "react";
import axios from "axios";
export const UserContext = React.createContext();
export function Provider({ children }) {
const getUsers = () => {
return axios.get(`https://randomuser.me/api/?results=10`).then((res) => {
return res;
});
};
return (
<UserContext.Provider value={{ usersList: getUsers() }}>
{children}
</UserContext.Provider>
);
}
users.js
-> Just including context where user data has been fetched and included react-select for dropdown.
-> Using useContext getting the promise value and inside useEffect hook getting the response and storing it in a state variable setUsers
-> In render method returning the select box values with the fetched users list as dropdown.
import React, { useContext, useEffect, useState } from "react";
import Select from "react-select";
import { UserContext } from "../context";
const Users = () => {
const { usersList } = useContext(UserContext);
const [users, setUsers] = useState([]);
const getUsers = () => {
usersList.then((users) => {
setUsers(users.data.results);
});
};
useEffect(() => {
getUsers();
}, []);
return (
<div>
<p> Below user list in select box is called from API </p>
<Select
value={""}
name="user"
options={users}
getOptionLabel={(option) => option.name.first}
getOptionValue={(option) => option.id.value}
className="basic-multi-select"
/>
</div>
);
};
export default Users;
Working example:
Query:
-> This works fine but in my real application this leads to multiple api calls.
-> I have checked in network tab and it has been called for at least 50 times and I feel that this will be a big issue regarding peroformance.
So I would like to know if there is a much better and standard way of implementing this in order to avoid memory leaks and multiple calls for an api fetch?
I am suspecting whether this line,
<UserContext.Provider value={{ usersList: getUsers() }}>
causing the real issue as I am calling getUsers() method with parathesis () but if I remove it the it doesn't get executed..
Please kindly help me and thanks in advance..
You can store the user list in an array, and have your components call getUsers on mount. Then just use users wherever you need
export function Provider({ children }) {
const [users, setUsers] = useState([]);
const getUsers = () => {
if (!users.length) {
axios.get(`https://randomuser.me/api/?results=10`).then((res) => {
setUsers(res.data.results);
});
}
};
return (
<UserContext.Provider value={{ usersList: users, getUsers }}>
{children}
</UserContext.Provider>
);
}
On User.js
const Users = () => {
const { usersList, getUsers } = useContext(UserContext);
useEffect(() => {
getUsers();
}, [getUsers]);
return (
<div>
<p> Below user list in select box is called from API </p>
<Select
value={""}
name="user"
options={users}
getOptionLabel={(option) => option.name.first}
getOptionValue={(option) => option.id.value}
className="basic-multi-select"
/>
</div>
);
};
Related
I wanted to prevent losing state on page refresh while being on a different route path. Im curious why the first example does not work. From what i understand when app mounts first thing that gonna render is component itself and then useEffects run. Since i got 3 here, first fetches and saves the data to the invoiceList state and then next useEffect that run should fill localStorage key with invoiceList state data. The last one obviously retrieve the data.
The second one does fill the "invoiceData" localStorage key with an empty array. Why is this happening if the invoiceList state already have the data after the first useEffect?
The second example that i provided works. I removed second useEffect and set localStorage key in the first useEffect with response data that i get from fetch.
I also wonder if im doing everything correct here. Any feedback appreciated :)
First example (not working):
import { ReactElement, useEffect, useState } from "react";
import { Outlet } from "react-router-dom";
import { Bar } from "../../components/Bar/Bar";
import { Invoice } from "./Root.utils";
type Props = {};
const Root = (props: Props): ReactElement => {
const [invoiceList, setInvoiceList] = useState<Invoice[]>([]);
useEffect(() => {
const fetchData = async () => {
const response = await fetch("./data.json");
const data = await response.json();
setInvoiceList(data);
};
fetchData();
}, []);
useEffect(() => {
window.localStorage.setItem("invoiceData", JSON.stringify(invoiceList));
}, []);
useEffect(() => {
setInvoiceList(
JSON.parse(window.localStorage.getItem("invoiceData") || "[]")
);
}, []);
return (
<div>
<Bar />
<Outlet context={{ invoiceList }} />
</div>
);
};
export default Root;
Second example (working):
import { ReactElement, useEffect, useState } from "react";
import { Outlet } from "react-router-dom";
import { Bar } from "../../components/Bar/Bar";
import { Invoice } from "./Root.utils";
type Props = {};
const Root = (props: Props): ReactElement => {
const [invoiceList, setInvoiceList] = useState<Invoice[]>([]);
useEffect(() => {
const fetchData = async () => {
const response = await fetch("./data.json");
const data = await response.json();
window.localStorage.setItem("invoiceData", JSON.stringify(data));
setInvoiceList(data);
};
fetchData();
}, []);
useEffect(() => {
setInvoiceList(
JSON.parse(window.localStorage.getItem("invoiceData") || "[]")
);
}, []);
return (
<div>
<Bar />
<Outlet context={{ invoiceList }} />
</div>
);
};
export default Root;
The first example is never storing the data into the localStorage because the fetch is an asynchronous function that and you are writing basically always the empty array into your localStorage.
The order of execution in the first example will be:
fetchData called
window.localStorage.setItem("invoiceData", JSON.stringify(invoiceList)); <- still empty array
setInvoiceList(JSON.parse(window.localStorage.getItem("invoiceData") || "[]"));
response.json() called
setInvoiceList(data); called
I would also recommend to improve your code a little like that:
import React, { useEffect, useState } from "react";
import { Outlet } from "react-router-dom";
import { Bar } from "../../components/Bar/Bar";
import { Invoice } from "./Root.utils";
const Root: React.FC = () => {
const [invoiceList, setInvoiceList] = useState<Invoice[]>([]);
useEffect(() => {
setInvoiceList(
JSON.parse(window.localStorage.getItem("invoiceData") || "[]")
);
const fetchData = async () => {
const response = await fetch("./data.json");
const data = await response.json();
window.localStorage.setItem("invoiceData", JSON.stringify(data));
setInvoiceList(data);
};
fetchData();
}, []);
return (
<div>
<Bar />
<Outlet context={{ invoiceList }} />
</div>
);
};
export default Root;
You can use the Link component from react-router and specify to={} as an object where you specify pathname as the route to go to. Then add a variable e.g. data to hold the value you want to pass on. See the example below.
Using the <Link /> component:
<Link
to={{
pathname: "/page",
state: data // your data array of objects
}}
>
Using history.push()
this.props.history.push({
pathname: '/page',
state: data // your data array of objects
})
Using either of the above options you can now access data on the location object as per the below in your page component.
render() {
const { state } = this.props.location
return (
// render logic here
)
}
Introducing The Problem
I am beginner ReactJS learner developing a simple weather app using OpenWeather API. The app is designed to fetch data from two components: one that returns the current weather of the user input and another one that returns the weather forecast for the next 5 days.
When the city name is typed down into the input field, the following message appears on the console:
GET https://api.openweathermap.org/data/2.5/weather?q=undefined&units=metric&appid=${Api.key} 400 (Bad Request)
I do not know how to pass the data from Search Component into App Component. Seriously, I have tried a lot of alternatives but they have been unsuccessful. There are commented lines of code to show my last try so far.
(ignore ForecastWeather because this component is empty)
I know that all of you are quite busy folks, but I would appreciate the help in a respectful way. Even suggestions about what I have to study (e.g. callBack) are welcome. I've tried this already:
https://stackoverflow.com/questions/56943427/whether-to-save-form-input-to-state-in-onchange-or-onsubmit-in-react
https://sebhastian.com/react-onchange/
The code is forward below:
App.js
import React, { useState } from "react";
import { Api } from "./Api";
import {
Search,
CurrentWeather,
ForecastWeather,
Footer,
} from "./components/index";
import "./App.css";
function App() {
const [getCity, setGetCity] = useState();
const [weatherData, setWeatherData] = useState(null);
const [forecastData, setForecastData] = useState(null);
const handleSearchLocation = (dataSearch) => {
const weatherDataFetch = fetch(
`${Api.url}/weather?q=${getCity}&units=metric&appid=${Api.key}`
);
const forecastDataFetch = fetch(
`${Api.url}/forecast?q=${getCity}&units=metric&appid=${Api.key}`
);
Promise.all([weatherDataFetch, forecastDataFetch])
.then(async (response) => {
const weatherResponse = await response[0].json();
const forecastResponse = await response[1].json();
setGetCity(dataSearch);
setWeatherData(weatherResponse);
setForecastData(forecastResponse);
})
.catch(console.log);
};
return (
<div className="App">
<Search
searchResultData={handleSearchLocation}
textPlaceholder="Search for a place..."
/>
{weatherData && <CurrentWeather resultData={weatherData} />}
<ForecastWeather resultData={forecastData} />
<Footer />
</div>
);
}
export default App;
Search.jsx
import React, { useState } from "react";
function Search({ textPlaceholder, searchResultData }) {
const [searchCity, setSearchCity] = useState("");
//const handlerOnChange = ( event, dataSearch ) => {
//setSearchCity(event.target.value);
//setSearchCity(dataSearch);
//searchResultData(dataSearch);
//};
return (
<div className="componentsBoxLayout">
<input
value={searchCity}
//onChange={handlerOnChange}
onChange={(event) => setSearchCity(event.target.value)}
onKeyDown={(event) => event.key === "Enter" && searchResultData(event)}
placeholder={textPlaceholder}
/>
</div>
);
}
export default Search;
CurrentWeather.jsx
import React from "react";
function CurrentWeather({ resultData }) {
return (
<div className="componentsBoxLayout">
<p>{resultData.name}</p>
</div>
);
}
export default CurrentWeather;
ForecastWeather.jsx (empty)
import React from 'react';
function ForecastWeather() {
return (
<div className="componentsBoxLayout">ForecastWeather</div>
)
}
export default ForecastWeather;
Api.js
const Api = {
url: "https://api.openweathermap.org/data/2.5",
key: "etcetc",
img: "https://openweathermap.org/img/wn",
};
export { Api };
Yippee-ki-yay
You can not use getCity in this function:
const handleSearchLocation = (dataSearch) => {
const weatherDataFetch = fetch(
`${Api.url}/weather?q=${getCity}&units=metric&appid=${Api.key}`
);
const forecastDataFetch = fetch(
`${Api.url}/forecast?q=${getCity}&units=metric&appid=${Api.key}`
);
Promise.all([weatherDataFetch, forecastDataFetch])
.then(async (response) => {
const weatherResponse = await response[0].json();
const forecastResponse = await response[1].json();
setGetCity(dataSearch);
setWeatherData(weatherResponse);
setForecastData(forecastResponse);
})
.catch(console.log);
};
getCity is defined on that function so it does not exist when you try to use it, unless you need getCity later for another component I would delete it becuase is redundant and do this:
const handleSearchLocation = (dataSearch) => {
const weatherDataFetch = fetch(
`${Api.url}/weather?q=${dataSearch}&units=metric&appid=${Api.key}`
);
const forecastDataFetch = fetch(
`${Api.url}/forecast?q=${dataSearch}&units=metric&appid=${Api.key}`
);
Promise.all([weatherDataFetch, forecastDataFetch])
.then(async (response) => {
const weatherResponse = await response[0].json();
const forecastResponse = await response[1].json();
setWeatherData(weatherResponse);
setForecastData(forecastResponse);
})
.catch(console.log);
};
When you run searchResultData on the search component you send the city you are looking for. Remember that useState will trigger a re-render but a function that is already running before that will never get the new value of the state if the state changes
I am making MERN social media app.
I want to show all the friends of the current user in a list in SideBar.jsx .
Home.jsx (parent of Sidebar.jsx)
import React, { Component } from "react";
import { Person } from "#material-ui/icons";
import Topbar from "../../components/topbar/Topbar";
import Sidebar from "../../components/sidebar/Sidebar";
import Feed from "../../components/feed/Feed";
import Rightbar from "../../components/rightbar/Rightbar";
import "./home.css";
export default function Home() {
return (
<>
<Topbar />
<div className="homeContainer">
<Sidebar />
<Feed />
<Rightbar />
</div>
</>
);
}
SideBar.jsx
import "./sidebar.css";
import React, { Component, useContext, useState } from "react";
...
import { axiosInstance } from "../../config";
export default function Sidebar() {
const { user } = useContext(AuthContext);
const [followings, setFollowings] = useState([]);
const followingsList = user.followings;
useEffect(() => {
const fetchFollowings = async () => {
followingsList.map(async (id) => {
try {
const theUser = await axiosInstance.get(`/users?userId=${id}`);
if (followings.includes(theUser.data)) {
} else {
setFollowings((prev) => [...prev, theUser.data]);
}
} catch (error) {
console.log(error);
}
});
};
fetchFollowings();
}, [user]);
return (
<div className="sidebar">
.....
<ul className="sidebarFriendList">
{followings.map((u) => (
<CloseFriend key={u._id} user={u} />
))}
</ul>
</div>
</div>
);
}
For example, in this case, in the state "followings", there are 2 user objects.
So, the line
followings.map((u) => (...
should only show 2 entries.
However, the result is below.
As you can see, it is showing each friend twice.
I tired to check if a user object already exists in followings by doing
if (followings.includes(theUser.data)) {
} else {
setFollowings((prev) => [...prev, theUser.data]);
}
But this is not working.
How can I make sure that it only shows each user once?
I want it to be like this
Any help would be greatly appreciated. thank you
This is happening because it seems that your useEffect method is being fired two times (probably because you are using React.StrictMode) and you are setting the state inside the .map method (that is not good because you trigger a new render each time you call the setState).
What I would recommend you to do, is to remove the setState from the .map method and just set the new state after you format your data. So it would be something like this:
const newFollowings = followingsList.map(async (id) => {
try {
const theUser = await axiosInstance.get(`/users?userId=${id}`);
return theUser.data;
} catch (error) {
console.log(error);
}
});
setFollowings(newFollowings);
Probably you would have to add a filtering to the array in case there are some errors (because on errors the mapped value would be undefined):
.filter(data => data);
When you are using the .map function with async/await Promise.all usually always does the trick. Instead of pushing the state on every iteration you collect the followers list and set the state when all your fetching is done. I did not test it yet, but I hope it works.
const followingsList = user.followings;
useEffect(() => {
const fetchFollowings = async () => {
const list = await Promise.all(followingsList.map(async (id) => (
await axios.get('/user?userId=' + id);
)));
setFollowers(list);
};
fetchFollowings();
}, [user]);
Note: let me know if it works, if not I'll do a little sandbox on my own
I'm trying to show data from an API call. The structure of the application looks like
MainComponent -> RefreshButton (this will fetch the data)
MainComponent -> ShowData (this will show the data that is being fetched)
MainComponent has a state userData that will store the response that was received from the API. Now the issue is, whenever I'm clicking the button, it is getting into an infinite loop of rendering and calls the API infinite times.
This is what the error shows:
Here is my MainComponent -
import React, { useEffect, useState } from "react";
import RefreshButton from "./RefreshButton";
import ShowData from "./ShowData";
const MainComponent = () => {
const [userData, setUserData] = useState();
useEffect(() => {
console.log(userData);
}, [userData]);
return (
<div>
<p style={{ textAlign: "center" }}>Main Component</p>
<RefreshButton setUserData={setUserData} />
{userData && <ShowData userData={userData} />}
</div>
);
};
export default MainComponent;
Here is my RefreshButton component -
import React from "react";
import axios from "axios";
const RefreshButton = ({ setUserData }) => {
const getData = () => {
axios
.get(`https://jsonplaceholder.typicode.com/todos`)
.then((response) => {
if (response.status === 200) setUserData(response.data);
})
.catch((err) => {
console.log(err);
});
};
return (
<div className="button-container">
<button className="fetch-data-button" onClick={() => getData()}>
Fetch new data
</button>
</div>
);
};
export default RefreshButton;
And here is my ShowData component -
import React from "react";
const ShowData = ({ userData }) => {
console.log("Here", userData);
return (
<>
{userData.map((info, idx) => (
<div className="user-data" key={idx}>
{info}
</div>
))}
</>
);
};
export default ShowData;
PS - I'm new to React and couldn't find a potential solution on this, there are several tutorials on how to fetch data from API calls and show it, but I wanted to know what I'm doing wrong here. Thanks in advance!
You might have misunderstood with the infinite loop error
It's actually a render error as being shown here:
To fix your render error, simply put an actual string variable in the {}
Because the response was an array of this object, so you can't simply render the whole object but need to pick an actual string variable inside:
[{
"userId": 1,
"id": 1,
"title": "delectus aut autem",
"completed": false
}],
Change to something like this:
const ShowData = ({ userData }) => {
console.log("Here", userData);
return (
<>
{userData.map((info, idx) => (
<div className="user-data" key={idx}>
{info.title} // <-- Put a title here.
</div>
))}
</>
);
};
Remove
useEffect(() => {
console.log(userData);
},[userData])
This will reevaluate component whenever user data changes, which Leeds to call showData infinitely
I am using firebase firestore and i fetched the data , everything is working fine but when i am passing it to some component only one item gets passed but log shows all the elements correctly.
I have just started learning react , any help is appreciated.
import React, { useEffect, useState } from 'react'
import { auth, provider, db } from './firebase';
import DataCard from './DataCard'
function Explore() {
const [equipmentList, setEquipments] = useState([]);
const fetchData = async () => {
const res = db.collection('Available');
const data = await res.get();
data.docs.forEach(item => {
setEquipments([...equipmentList, item.data()]);
})
}
useEffect(() => {
fetchData();
}, [])
equipmentList.forEach(item => {
//console.log(item.description);
})
const dataJSX =
<>
{
equipmentList.map(eq => (
<div key={eq.uid}>
{console.log(eq.equipment)}
<p>{eq.equipment}</p>
</div>
))
}
</>
return (
<>
{dataJSX}
</>
)
}
export default Explore
You have problems with setting fetched data into the state.
You need to call setEquipments once when data is prepared because you always erase it with an initial array plus an item from forEach.
The right code for setting equipment is
const fetchData = async () => {
const res = db.collection('Available');
const data = await res.get();
setEquipments(data.docs.map(item => item.data()))
}