Develop Reference

My API data is not being rendered with React

I'm learning React by making a Spotify clone and for now, what I'm trying to do is to show Spotify sections such as "last played songs", "top artists" and "top songs" through a component called Body.js.
I get the data from a Spotify official API library created by jmperez in a useEffect hook in the App.js component. Once I get the data from the API, I store it in an object called initialState in a file called reducer.js.
This reducer.js file contains the initial state and the reducer function for a custom hook called useDataLayer.js which is a useContext hook that passes as value a useReducer to all the branches of my program. This way what I do is update the initialState from App.js and access this object through the useDataLayer hook in the different branches of my program (among them the Body component).
The problem I am having now is that it is not rendering the three sections mentioned before in Spotify, but only shows me one which is the "top songs". The weird thing is that for a second it does render the other components as if it was getting the data and rendering but then it updates and they disappear. Please if someone can help me with this problem and explain to me why this happens it would be great.
App.js code
import React, {useState, useEffect} from 'react';
import Login from './components/Login';
import Player from './components/Player';
import { getTokenFromResponse } from './spotify';
import './styles/App.scss';
import SpotifyWebApi from "spotify-web-api-js";
import { library } from '#fortawesome/fontawesome-svg-core';
import { fas } from '#fortawesome/free-solid-svg-icons';
import { fab } from '#fortawesome/free-brands-svg-icons';
import { useDataLayer } from './components/Hooks/useDataLayer';
library.add(fas, fab);
//spotify library instance
const spotify = new SpotifyWebApi();
function App() {
const [token, setToken] = useState(null);
const [{ user }, dispatch] = useDataLayer();
// where I get the necessary data from the api
useEffect(() => {
// function to get access token
let accessToken = getTokenFromResponse();
window.location.hash = '';
if(accessToken){
spotify.setAccessToken(accessToken);
setToken(accessToken);
//FROM HERE I GET THE DATA I NEED
// here I get the data of my user
spotify.getMe().then((data) =>{
dispatch({
type: "GET_USER",
user: date
})
});
spotify.getUserPlaylists().then((data) => {
dispatch({
type: "GET_PLAYLISTS",
playlists: dates
})
});
spotify.getMyTopTracks({limit: 4}).then((data) => {
dispatch({
type: "GET_TOP_TRACKS",
top_tracks:data,
})
});
spotify.getMyRecentlyPlayedTracks({limit: 4}).then((data) => {
dispatch({
type: "RECENTLY_PLAYED",
recently_played: date,
})
});
spotify.getMyTopArtists({limit: 4}).then((data) => {
dispatch({
type: "GET_TOP_ARTISTS",
top_artists: date,
})
});
}
}, [token])
//if the token is valid enter Player.js where Body.js is inside and if not return to the login component
return (
<div className="App">
{ token ? <Player spotify= {spotify} /> : <Login />}
</div>
);
}
export defaultApp;
Body.js code
import React from 'react'
import '../styles/Body.scss'
import { useDataLayer } from "./Hooks/useDataLayer.js";
import { FontAwesomeIcon } from '#fortawesome/react-fontawesome';
function Body({ spotify }) {
//get the properties of the necessary data that I want to display in this component with useDataLayer
const [{ spotify_recommendations, recently_played, top_tracks, top_artists }, dispatch] = useDataLayer();
return (
<div className= "main-body">
<div className= "body-option">
<span className= "see-more">See All</span>
<FontAwesomeIcon icon={['fas', 'arrow-right']} />
<div>
{
//to show the image and info of the track
recently_played?.items.map((item, index) =>{
return (
<div className= "track" key= {index}>
<img src= {item.track.album.images[1].url} alt= "recently played track"></img>
<div className= "track-data">
<h3>{item.track.name}</h3>
<p>{item.track.artists.map(artist => artist.name).join(", ")}</p>
</div>
</div>
)
})
}
</div>
</div>
<div className= "body-option">
<span className= "see-more">See All</span>
<FontAwesomeIcon icon={['fas', 'arrow-right']} />
<div>
{
//to show the image and info of the track
top_tracks?.items.map((topArtist, index) => {
return (
<div className= "track" key= {index}>
<img src= {topArtist.album.images[1].url} alt= "recently played track"></img>
<div className= "track-data">
<h3>{topArtist.name}</h3>
<p>{topArtist.artists.map(artist => artist.name).join(", ")}</p>
</div>
</div>
)
})
}
</div>
</div>
<div className= "body-option">
<span className= "see-more">See All</span>
<FontAwesomeIcon icon={['fas', 'arrow-right']} />
<div>
{
//to show the image and info of the artist
top_artists?.items.map((topTrack, index) => {
return (
<div className= "track" key= {index}>
<img src= {topTrack.images[1].url} alt= "recently played track"></img>
<div className= "track-data">
<h3>{topTrack.name}</h3>
<p>{topTrack.genres.join(", ")}</p>
</div>
</div>
)
})
}
</div>
</div>
</div>
)
}
export default Body
Code of my custom hook useDataLayer.js
import React, {useContext, createContext, useReducer} from 'react'
let DataContext = createContext();
export function DataLayer({reducer, initialState, children}) {
return (
<DataContext.Provider value= {useReducer(reducer, initialState)}>
{children}
</DataContext.Provider>
)
}
export let useDataLayer = () => useContext(DataContext);
SideBar.js: the component where i display the user's playlist
import React from 'react';
import { FontAwesomeIcon } from '#fortawesome/react-fontawesome';
import { useDataLayer } from './Hooks/useDataLayer.js';
import '../styles/SideBar.scss';
function SideBar({ spotify }){
const [{ playlists }, dispatch] = useDataLayer();
return (
<div className= "side-bar">
<div className= "side-bar-options">
<div className= "spotify-logo">
<FontAwesomeIcon icon={['fab', 'spotify']} size= "3x"/>
<h1 className= "spotify-title">Spotify</h1>
</div>
<a className= "option" href= "./Player.js">
<FontAwesomeIcon icon={['fas', 'home']} />
<p className= "option-title" >Inicio</p>
</a>
<a className= "option" href= "./Player.js">
<FontAwesomeIcon icon={['fas', 'search']} />
<p className= "option-title">Buscar</p>
</a>
<a className= "option" href= "./Player.js">
<FontAwesomeIcon icon={['fas', 'headphones']} />
<p className= "option-title" >Tu Biblioteca</p>
</a>
</div>
<p className= "playlist-title">PLAYLISTS</p>
<div className= "playlists">
{
playlists?.items?.map(
(list, index) =>
<p className="playlists-option"
key={index}
>
{list.name}
</p>
)
}
</div>
</div>
)
}
export default SideBar;
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
Player.js
import React from 'react';
import "../styles/Player.scss";
import SideBar from "./SideBar.js";
import Body from "./Body.js";
function Player({spotify}) {
return (
<div className= "player-container">
<div className= "player_body">
<SideBar spotify= {spotify} />
<Body spotify= {spotify} />
</div>
</div>
)
}
export default Player;
spotify.js: the code where i get the token from the URL
const authEndpoint = "https://accounts.spotify.com/authorize";
const clientId = '84c134b175474ddabeef0e0b3f9cb389'
const redirectUri = 'http://localhost:3000/'
const scopes = [
"user-read-currently-playing",
"user-read-recently-played",
"user-read-playback-state",
"user-top-read",
"user-modify-playback-state",
"user-follow-modify",
"user-follow-read",
"playlist-modify-public",
"playlist-modify-private",
"playlist-read-private",
"playlist-read-collaborative"
];
//obtain acces token from url
export const getTokenFromResponse = () => {
let params = new URLSearchParams(window.location.hash.substring(1));
let token = params.get("access_token");
return token;
};
//acces url
const accessUrl = `${authEndpoint}?client_id=${clientId}&redirect_uri=${redirectUri}&scope=${scopes.join("%20")}&response_type=token&show_dialog=true`;
export default accessUrl;
Thank you very much for your time and attention.

By the look of it, your useEffect hook is being called twice in quick succession. It has the dependency of token, which starts as null for your first render. Inside the hook you then read the accessToken and set the state for it to your token. Doing this will trigger another render because the dependency changed from null to the value of your access token.
I would suggest to simply remove token from your useEffect dependency array (so that your hook acts as an "on mounted" event) and see if that gets you the desired effect. You should eventually move the getTokenFromResponse outside the hook, assuming it is not available on first render, as I'm just guessing it is immediately available.
Post comments, it might be better to separate your initializing code into a useEffect that only runs once, when the component is first mounted. This way, as I now suspect getTokenFromResponse() returns a new Object every call, you only need to call it once. Note, if it returns a Promise, this won't work, so you should verify this first before trying.
To better illustrate my point, I've put it in code with some comments:
useEffect(() => {
setToken(getTokenFromResponse());
// this only needs to happen once
window.location.hash = '';
}, []; // <- empty dependency array will only run once, on mount
useEffect(() => {
// out of the 2 times this will be called,
// it should only pass this condition on the last/2nd
if(token){
spotify.setAccessToken(token);
//FROM HERE I GET THE DATA I NEED
// here I get the data of my user
spotify.getMe().then((data) =>{
dispatch({
type: "GET_USER",
user: date
})
});
spotify.getUserPlaylists().then((data) => {
dispatch({
type: "GET_PLAYLISTS",
playlists: dates
})
});
spotify.getMyTopTracks({limit: 4}).then((data) => {
dispatch({
type: "GET_TOP_TRACKS",
top_tracks:data,
})
});
spotify.getMyRecentlyPlayedTracks({limit: 4}).then((data) => {
dispatch({
type: "RECENTLY_PLAYED",
recently_played: date,
})
});
spotify.getMyTopArtists({limit: 4}).then((data) => {
dispatch({
type: "GET_TOP_ARTISTS",
top_artists: date,
})
});
}
// this will trigger the effect any time token changes,
// which should now only be twice:
// 1st at it's default state value (null)
// 2nd after the previous useEffect sets its state
}, [token]);
Hope that helps but, if it's a promise, you'll need to handle it according (suggestion: moving the setToken into the then)
Good luck!

Forwarding props from parent to child component

I have 2 components list of posts and when clicking on link on post card i'm entering into post.
I can't access props.postDetails in child component. When I console log the props, I have {history: {…}, location: {…}, match: {…}, staticContext: undefined} only this without props.postDetails.
Can somebody help?
Code for parent component is:
mport {useState, useEffect} from 'react';
import {BrowserRouter as Router, Switch, Route, Link, withRouter} from "react-router-dom";
import logo from "./assets/images/logo.jpg";
import Post from './Post';
const Home = () => {
const [posts, setPosts] = useState([]);
useEffect(() => {
getResults();
},[]);
const getResults =() => {
fetch("https://blog-d8b04-default-rtdb.europe-west1.firebasedatabase.app/posts.json")
.then(response => response.json())
.then(data => {setPosts(data)});
}
const postsArr = [];
Object.values(posts).forEach((post, key) => {
postsArr.push(post);
});
return(
<div>
<div className="container-fluid">
<div className="row">
<div className="posts-container col-md-12">
<div className="row">
{
postsArr.map((post, key) => (
<div className="col-md-4">
<Link to={`/post/${key}`} >
<div className="pic-wrapper">
<img className="img-fluid" src={post.pic} alt={post.title}/>
</div>
<h4>{post.title}</h4>
<Post postDetails={post}/>
</Link>
</div>
))
}
</div>
</div>
</div>
</div>
</div>
)
}
Code for child component:
import {withRouter} from "react-router-dom";
const Post = (props) => {
const {pic, title, author, description} = props.postDetails;
return(
<div className="container">
<div className="pic-wrapper">
<img className="img-fluid" src={pic} alt={title}/>
</div>
<h4>{title}</h4>
<p>{author}</p>
</div>
)
}
export default withRouter(Post);

Issue
Ok, it's as I started to suspect. You are rendering a Post component in more than 1 place.
The issue here is that in Home.js you are passing a postDetails prop, (<Post postDetails={post.pic} />), but in app.js you are only passing the route props from Route, (<Route path="/post/:postId" exact strict component={Post} />). This Post component is the one triggering the error.
Solution
An easy solution is to simply pass the post data along with the route transition.
<Link
to={{
pathname: `/post/${key}`,
state: {
post
}
}}
>
...
<Post postDetails={post.pic} />
</Link>
And access the route state on the receiving end in Post. Try to read the post details from props first, and if they is falsey (null or undefined) assume it was passed in route state and access it there.
const Post = (props) => {
const { state } = props.location;
const { pic, title, author, description } = props.postDetails ?? state.post;
return (
<div className="container">
<div className="pic-wrapper">
<img className="img-fluid" src={pic} alt={title} />
</div>
<h4>{title}</h4>
<p>{author}</p>
</div>
);
};
Of course there is room to make this a bit more robust but this is a good start.
Additional Suggestion
Instead of saving post state that isn't formed correctly for what/how you want to render it, you can transform the response data before saving it into state. This save the unnecessary step of transforming it every time the component rerenders.
const getResults = () => {
setLoading(true);
fetch(
"https://blog-d8b04-default-rtdb.europe-west1.firebasedatabase.app/posts.json"
)
.then((response) => response.json())
.then((data) => {
setPosts(Object.values(data));
setLoading(false);
});
};
Then map as per usual. Make sure to place the React key on the outer-most mapped element, the div in your case.
{posts.map((post, key) => (
<div className="col-md-4" key={key}>
...
</div>
))}
Demo

That is indeed an expected behaviour, because you are actually mapping what appears to be an empty array - see postArr; on your first render it will result as an empty array and since that's not a state, it will never re render your child component with the appropriate props.
I don't really see why you fetch the data, set them to your posts useState and then copy them over to a normal variable; Instead, remove your postArr and on the map replace it with your posts directly.
Since that's a state, react will listen to changes and rerender accordingly, fixing your problem

React - Add user to list of Favorites

I have a simple user list with several details from the following api: https://gorest.co.in/public-api/users, where I want to add a selected user to a list of favorites. I am working with react-router to navigate between pages. Is this possible with React or do I also need Redux?
I have a complete LIVE EXAMPLE here with the user page and favorites.
Here is the code below for the user list:
import React from "react";
import axios from "axios";
import NavLinks from "./components/navLink";
export default class UserList extends React.Component {
constructor(props) {
super(props);
this.state = {
list: [],
addToFav: false
};
this.list = [];
}
componentDidMount() {
this.getList();
}
/* get users list */
getList = async () => {
const api =
"https://gorest.co.in/public-api/users?_format=json&access-token=3qIi1MDfD-GXqOSwEHHLH73Y3UitdaFKyVm_";
await axios
.get(api)
.then(response => {
this.list = response.data.result;
this.setState({
list: this.list
});
})
.catch(err => {
console.log(err);
});
};
addToFav = () => {
this.setState(
{
addToFav: !this.state.addToFav
},
() => console.log(this.state.addToFav)
);
};
render() {
let style = {
display: "grid",
gridTemplateColumns: "repeat(auto-fill, minmax(250px, 1fr))",
padding: "1rem",
gridGap: "1rem 1rem"
};
return (
<div>
<NavLinks />
<ul style={style}>
{this.state.list.map(user => {
return (
<li key={user.id}>
<div>
<img className="thumb" alt="" src={user._links.avatar.href} />
</div>
<div className="userInfo">
<p>
{user.first_name} {user.last_name}
</p>
</div>
<button onClick={this.addToFav}>Add to Favorites</button>
</li>
);
})}
</ul>
</div>
);
}
}
Thank you!

Here's a working codesandbox: https://codesandbox.io/s/brave-fire-4kd4p
This train of thought pretty much follows what #Chris G mentioned. Have a top-level state that holds the list of users and the favorites list. Then pass those as props to the individual components.
App.js
Hit your API here instead of inside your UserList component to prevent any unnecessary re-renders.
import React, { Component } from "react";
import UserList from "./userList";
import FavoriteList from "./favoriteList";
import { BrowserRouter as Router, Switch, Route } from "react-router-dom";
import axios from "axios";
export default class App extends Component {
state = {
list: [],
favorites: []
};
addFavorite = favorite => {
const { favorites } = this.state;
if (!favorites.some(alreadyFavorite => alreadyFavorite.id == favorite.id)) {
this.setState({
favorites: [...this.state.favorites, favorite]
});
}
};
getList = async () => {
const api =
"https://gorest.co.in/public-api/users?_format=json&access-token=3qIi1MDfD-GXqOSwEHHLH73Y3UitdaFKyVm_";
await axios
.get(api)
.then(response => {
this.setState({
list: response.data.result
});
})
.catch(err => {
console.log(err);
});
};
componentDidMount() {
this.getList();
}
render() {
return (
<Router>
<Switch>
<Route
path="/"
exact
render={() => (
<UserList list={this.state.list} addFavorite={this.addFavorite} />
)}
/>
<Route
path="/favorites"
render={() => <FavoriteList favorites={this.state.favorites} />}
/>
</Switch>
</Router>
);
}
}
UserList.js
Call the addFavorite event-handler on button-click to pass that item back up to the parent-state.
import React from "react";
import NavLinks from "./components/navLink";
export default class UserList extends React.Component {
render() {
let style = {
display: "grid",
gridTemplateColumns: "repeat(auto-fill, minmax(250px, 1fr))",
padding: "1rem",
gridGap: "1rem 1rem"
};
return (
<div>
<NavLinks />
<ul style={style}>
{this.props.list.map(user => {
return (
<li key={user.id}>
<div>
<img className="thumb" alt="" src={user._links.avatar.href} />
</div>
<div className="userInfo">
<p>
{user.first_name} {user.last_name}
</p>
</div>
<button onClick={() => this.props.addFavorite(user)}>
Add to Favorites
</button>
</li>
);
})}
</ul>
</div>
);
}
}
Favorite.js
Use the favorites array that was passed in as a prop and iterate over it.
import React from "react";
import NavLinks from "./components/navLink";
export default class FavoriteList extends React.Component {
constructor(props) {
super(props);
this.state = {};
}
render() {
const { favorites } = this.props;
return (
<div>
<NavLinks />
<ul>
{favorites.map(user => {
return (
<li key={user.id}>
<div>
<img className="thumb" alt="" src={user._links.avatar.href} />
</div>
<div className="userInfo">
<p>
{user.first_name} {user.last_name}
</p>
</div>
</li>
);
})}
</ul>
</div>
);
}
}

Is this possible with React or do I also need Redux?
Most if not all of those problems can be solved without redux just by using component state. It just gets increasingly difficult to pass the state to the components needing it the more global state you have and the more components at different depth need to access and update it.
In your case it might be sufficient to store the favorites in a component state high up the tree and pass it to the components consuming it. You could either pass it directly to the components or you could use react context to make it accessible to components deep in the tree.
A simple example:
const FavoritesContext = React.createContext({favorites: []});
const FavoritesProvider = ({children}) => {
const [favorites, setFavorites] = useState([]);
const add = useCallback(favorite => setFavorites(current => [...current, favorite]), [setFavorites]);
return (
<FavoritesContext.Provider value={{favorites, add}}>
{children}
</FavoritesContext.Provider>
};
You can use it like that:
<FavoritesProvider>
<MyApp />
</FavoritesProvider>
then anywhere in a component in your app:
const MyComponent = () => {
const {favorites, add} = useContext(FavoritesContext);
const [draft, setDraft] = useState('');
const handleChange = event => setDraft(event.target.value);
const handleAdd = () => {
add(draft);
setDraft('');
};
return (
<div>
<ul>
{favorites.map(favorite => <li>{favorite}</li>)}
</ul>
<input value={draft} type="text" onChange={handleChange} />
<button onClick={handleAdd}>Add</button>
</div>
);
}
In this simple example the favorites are just text but they could as well be objects. Also it demonstrates how you could provide a handler for adding a favorite. You could implement e.g. a handler for removing favorites in the same way.
Persisting your favorites is yet another topic you may need to deal with. You could use e.g. localStorage for that or you could store that in a database on a server and fetch it when your app mounts the first time.

I have changed your file a bit take a look - https://codesandbox.io/s/clever-butterfly-vb2iz

One way is to use the localstorage of browser.
But this way is slighty expensive and synchronous.
Update the list whenever the favorited item status is changed via
localStorage.setItem('users',JSON.stringify(users));
And look for the favorited items via
localStorage.getItem('users');//You need to parse this by JSON.parse()
Maintain a isFavorite variable in the object list.
let users=[{name:"Mr.A",isFavorite:false},{name:"Mr.B",isFavorite:true},...];
On the click of favoriting button this.addToFav change it as follows
addToFav=user=>{
const {users}=this.state;
this.setState({
users:users.map(userObject=>userObject.id===user.id?
{...userObject,isFavorite:!userObject.isFavorite}:user)
},()=>{saveToLocal(this.state.users)});
}
Now you can access the favorite items even if the page is reloaded and stays there till you clear the storage.Use this localStorage.clear() for that.

First I would change your onClick to this:
<button onClick={() => this.addToFav(user.id)}>Add to Favorites</button>
This will allow you to pass the id to the addToFave function.
Then I would add a new state called faves (an array) and every time someone clicks the add button I would add their id into this array. This will allow you to filter your original list when you want to display the faves.
this.state = {
list: [],
faves: [],
};
}
addToFav = (id) => {
this.setState(prevState => ({
faves: [...prevState.faves, id],
}));
};
When I want to use the list of faves instead of the normal list I would do this:
const favesList = [];
this.state.list.map(listItem =>
this.state.faves.find(
faveId => listItem.id === faveId
) && favesList.push(item);
Then I would pass that to the faves component

I changed accordingly, please try
https://codesandbox.io/s/youthful-poincare-7oeh0
the key is you can use push state to your link like below
<Link to={{ pathname: "/favorites", state: { favList: this.props.favList }}} onClick={() => this.forceUpdate()}>
later on under your fav page call to retrieve the state
this.props.location.state.favList

i have changed the code a little by using react context.
I would not use redux for this cause i think it would be a overkill.
Anyways here is the updated sandbox...
Link for sandbox

TypeError: Cannot read property of undefined using React

I'm new in React and I'm doing a little app with PokeAPI. I have a component called PokemonDetail in which I want to show the details of a pokemon, but the app throws me the next error
TypeError: Cannot read property 'front_default' of undefined
my component looks like this:
import React from "react";
const PokemonDetail = ({ pokemon }) => {
return (
<div>
<div className="text-center">{pokemon.name}</div>
<img src={pokemon.sprites.front_default} alt={pokemon.name} />
{pokemon.id}
</div>
);
};
export default PokemonDetail;
And the App component from which the PokemonDetail recive the prop of pokemon looks like this:
import React from "react";
import PokeAPI from "../apis/PokeAPI";
import SearchBar from "./SearchBar";
import PokemonDetail from "./PokemonDetail";
class App extends React.Component {
state = { pokemon: '' };
onTermSubmit = async term => {
try {
const response = await PokeAPI.get(`pokemon/${term}`);
this.setState({ pokemon: response.data });
console.log(response);
} catch (error) {
console.log("No existe");
}
};
render() {
return (
<div className="container">
<div className="row mt-3">
<div className="col">
<SearchBar onFormSubmit={this.onTermSubmit} />
</div>
</div>
<div className="row mt-3">
<div className="col-9" />
<div className="col-3">
<PokemonDetail pokemon={this.state.pokemon} />
</div>
</div>
</div>
);
}
}
export default App;
I don't understand why it throws me this error because only throws it with this and other properties of the json. With the name property works and wait until I send it some props, same with the id but no with the front_default property, which is a url of a image.

Because ajax is slower than react rendering, you can use a loading component before you get the data.
const PokemonDetail = ({ pokemon }) => {
if(pokemon.sprites == undefined){
return(
<div>
Loading...
</div>
);
}
return (
<div>
<div className="text-center">{pokemon.name}</div>
<img src={pokemon.sprites.front_default} alt={pokemon.name} />
{pokemon.id}
</div>
);
};

Very likely just an AJAX issue, your component renders before it has time to complete your request to the API. Try adding an additional check before rendering the image.
import React from "react";
const PokemonDetail = ({ pokemon }) => {
return (
<div>
<div className="text-center">{pokemon.name}</div>
{pokemon.sprites ? (
<img src={pokemon.sprites.front_default} alt={pokemon.name} />
) : (
null
)
}
{pokemon.id}
</div>
);
};
export default PokemonDetail;

#ZHAOXIANLONG gave you the best solution (use a loading component until you receive data), but, if you do not use a loading component, you can use the get method from lodash library [1] in order to avoid a possible error.
import React from "react";
import _ from 'lodash';
const PokemonDetail = ({ pokemon }) => {
const front_default = _.get(pokemon, 'sprites.front_default', 'DEFAULT_VALUE');
const name = _.get(pokemon, 'name', 'DEFAULT_VALUE');
return (
<div>
<div className="text-center">{pokemon.name}</div>
<img src={pokemon.sprites.front_default} alt={pokemon.name} />
{pokemon.id}
</div>
);
};
export default PokemonDetail;
where the third parameter ('DEFAULT_VALUE') is a default value that will be used if the lodash can not retrieve a value for your query.
PS: I advise you to use lodash even in #ZHAOXIANLONG solution if you know that your API Server can be changed.
[1] https://lodash.com/docs/4.17.11#get

The initial state is { pokemon: '' }; pokemon is an empty string. PokemonDetail is referring to pokemon.sprites.front_default, but pokemon is initially a string and a string does not have a field called sprites.
If you are expecting pokemon to eventually become an object, you could initialize it to something that looks like an object:
state = { pokemon: { sprites: {front_default: '' }}};

Getting error "dispatch is not a function" when combining two files [ReactJS]

I am creating a todo List application using reactJS. If I write two different logic in two separate files it works just fine but while combining those two files it gives an error.
RenderRemaining.js file:
import React from 'react';
import { connect } from 'react-redux';
import store from '../store/store';
import RenderRemainingData from './RenderRemainingData';
const RenderRemaining = (props) => {
return (
<div>
<h2>Tasks: </h2>
<hr />
{props.list.map((detail) => {
return <RenderRemainingData key={detail.id} {...detail} />
})}
</div>
);
}
const mapStateToProps = (state) => {
return {
list: state.todoReducer
};
}
export default connect(mapStateToProps)(RenderRemaining);
RenderRemainingData.js file:
import React from 'react';
import { connect } from 'react-redux';
import removeTodo from '../actions/removeTodo';
const RenderRemainingData = ({ dispatch, todo, id, description, isCompleted }) => {
if (!isCompleted) {
return (
<div key={id}>
<h4>{todo}
<span className="float-right">
<a href="#" title="Remove" onClick={() => {
dispatch(removeTodo({todo, description, id}));
}}><i className="fas fa-times"></i></a>
</span>
</h4>
<p>{description}</p>
</div>
);
}
return false;
}
export default connect()(RenderRemainingData);
Now above code works just fine.
After combining above two files as one js file in RenderRemaining.js and deleting RenderRemainingData.js file.
RenderRemaining.js file: (after combining)
import React from 'react';
import { connect } from 'react-redux';
import store from '../store/store';
import removeTodo from '../actions/removeTodo';
const RenderRemainingData = ({ dispatch, todo, id, description, isCompleted }) => {
if (!isCompleted) {
return (
<div key={id}>
<h4>{todo}
<span className="float-right">
<a href="#" title="Remove" onClick={() => {
dispatch(removeTodo({todo, description, id}));
}}><i className="fas fa-times"></i></a>
</span>
</h4>
<p>{description}</p>
</div>
);
}
return false;
}
const RenderRemaining = (props) => {
return (
<div>
<h2>Tasks: </h2>
<hr />
{props.list.map((detail) => {
return <RenderRemainingData key={detail.id} {...detail} />
})}
</div>
);
}
const mapStateToProps = (state) => {
return {
list: state.todoReducer
};
}
connect()(RenderRemainingData);
export default connect(mapStateToProps)(RenderRemaining);
Now when an event of onClick occurs it gives an error as dispatch is not a function in console.
I don't know why is this happening.

This is because when you are rendering the RenderRemainingData component inside RenderRemaining you are not passing the dispatch, but in case of separate file, component will receive the dispatch from connect.
Possible Solutions:
1- Pass the dispatch in props to RenderRemainingData component:
return <RenderRemainingData key={detail.id} {...detail} dispatch={props.dispatch} />
And remove this line:
connect()(RenderRemainingData);
2- Another possible solution is:
Use a wrapper component and instead of rendering RenderRemainingData render that Wrapper component. Like this:
const WrapperRenderRemainingData = connect()(RenderRemainingData);
return <WrapperRenderRemainingData key={detail.id} {...detail} />

Calling connect()(SomeRandomComponent) means you are calling a function which will return you a value, a new Component that you can use.
So in the case of two separate files, first you create a new Component with connect()(RenderRemainingData), then you export the return value.
These two are equivalent.
export default connect()(SomeRandomComponent)
and
const newComponent = connect()(SomeRandomComponent)
export default newComponent
Now, if we look at bottom of your file containing the combined code.
connect()(RenderRemainingData);
export default connect(mapStateToProps)(RenderRemaining);
First expression, creates a newComponent by wrapping connect around RenderRemainingData. But since you didn't assign the return value to a new identifier or RenderRemainingData( you can't because latter is a const , by the way). Also, when you pass a function as a parameter, it is passed by value, so altering the parameter function inside the calling function will not affect its usage outside the calling function.
Easiest Solution for you will be the one mentioned below.
const RenderRemainingData = connect()(props => {
///Add the implementation here
})
There you go, you have a connected component in the same file, with dispatch available.