How to dispatch to Reducer before React renders component? - reactjs

React newcomer here.
I'm loading Astronomy Picture of the Day in a component using a loading spinner.
I want the page to get data every time I call it from navbar but it's flashing old data before showing the spinner.
How to avoid this behavior? I don't want to use ComponentWillMount because it's deprecated and I'm using functions.
The component code:
import { useEffect, useContext } from 'react'
import { getApod } from '../context/nasa/NasaActions'
import NasaContext from '../context/nasa/NasaContext'
import Spinner from './layout/Spinner'
function Apod() {
const {loading, apod, dispatch} = useContext(NasaContext)
useEffect(() => {
dispatch({type: 'SET_LOADING'})
const getApodData = async() => {
const apodData = await getApod()
dispatch({type: 'SET_APOD', payload: apodData})
}
getApodData()
}, [dispatch])
const {
title,
url,
explanation,
} = apod
if (loading) { return <Spinner /> }
return (
<div>
<h2>{title}</h2>
<img src={url} className='apod' alt='apod'/>
<p>{explanation}</p>
</div>
)
}
export default Apod
Thanks for your time.
Edit: I deleted the repository. It's already answared correctly.

I suggest you another solution to keep your navbar clean.
You can declare an instance variable loaded using the useRef hook. This variable will be initialized to false and set to true as soon as the apod is dispatched to your store.
import { useContext, useRef } from 'react'
function Apod() {
const {apod, dispatch} = useContext(NasaContext)
const loaded = useRef(false);
const {title, url, explanation} = apod
useEffect(() => {
dispatch({type: 'SET_LOADING'})
const loadApod = async() => {
const apodData = await getApod()
loaded.current = true;
dispatch({type: 'SET_APOD', payload: apodData})
}
loadApod()
}, [dispatch])
if (!loaded.current) { return <Spinner /> }
return (
<div>
<h2>{title}</h2>
<img src={url} className='apod' alt='apod'/>
<p>{explanation}</p>
</div>
)
}
export default Apod;

I had an idea, to clean the object in Context using onClick on the navbar button.
Is this the best way? I don't know but it's working as I wanted.
import NasaContext from '../../context/nasa/NasaContext'
import { useContext } from 'react'
import { Link } from 'react-router-dom'
import logo from './assets/logo.png'
function Navbar() {
const {dispatch} = useContext(NasaContext)
const resetApod = () => {
const pathname = window.location.pathname
if ( pathname !== '/' ) {
dispatch({type: 'SET_APOD', payload: {}})
}
}
return (
<div className="navbar">
<div className="navbar-logo">
<img src={logo} alt='Experimentum'/>
</div>
<div className="navbar-menu">
<Link to='/' onClick={resetApod}>APOD </Link>
<Link to='/about'>ABOUT </Link>
</div>
</div>
)
}
export default Navbar

Related

Problem when rendering image in React component

I´m getting an error when trying to render an image in component.
I paste the code here.
Is it possible that I need a babel or webpack plugin?
In this component, the image rendering works fine:
import React from "react";
function ProductItem({ product }) {
return product ? (
<div>
<div>
<img src={product.images[0]} alt={product.title} />
</div>
<div>
{product.title}
<br />
${product.price}
</div>
<p>{product.description}</p>
</div>
) : <p>Loading Product... </p>;
};
export default ProductItem;
In this other component is where I have the problem.
ProductDetail.js
import React from "react";
import useGetProducts from "../hooks/useGetProducts";
const API = 'https://api.escuelajs.co/api/v1/products';
function ProductDetail() {
const data = useGetProducts(`${API}/6`);
return (
<>
{data.products
?
<>
<h3>{data.products.title}</h3>
<p>{data.products.description}</p>
<div>
<img src={data.products.images[0]} alt="title" />
</div>
</>
: <h4>Loading...</h4>
}
</>
);
}
export default ProductDetail;
Custom Hook with useEffect, the useGetProducts function is responsible for bringing the data from the API with the Axios library
import { useEffect, useState } from "react";
import axios from "axios";
const useGetProducts = (API) => {
const [products, setProducts] = useState([])
const [error, setError] = useState("");
const [loaded, setLoaded] = useState(false);
useEffect(() => {
(async () => {
try {
const response = await axios(API);
setProducts(response.data);
} catch (error) {
setError(error.message);
} finally {
setLoaded(true);
}
})();
}, []);
return { products, error, loaded };
};
export default useGetProducts
Your default state for products is [], so the conditional render data.products in ProductDetail.js always return true so you can change default state for products is null
const [products, setProducts] = useState(null);
The first answer is correct, so I will not duplicate it, but I see room for improvement in your code/example.
Your useGetProducts hook is very easy to break and hard to reuse. If you will pass the wrong URL or the structure of the API will change it will break your code. Also, the hook is not very generic, cause you will need to create similar fn for each entity. My suggestion. Use react-query and separate functions for calling API. So it will look like this.
import { useQuery } from 'react-query'
import axios from 'axios'
export default function ProductPage() {
const productResponse = useQuery('exchanges', () => getProduct('6'))
const { isLoading, isError, data: product } = productResponse
return (
<div>
{isLoading && <div>Loading...</div>}
{isError && <div>Something went wrong :(</div>}
{product && (
<div>
<h1>Product title: {product.title}</h1>
<p>
{product.images.map(imageSrc => (
<img key={imageSrc} src={imageSrc} alt="" />
))}
</p>
</div>
)}
</div>
)
}
interface Product {
id: string
title: string
images: string[]
}
function getProduct(id: string): Promise<Product> {
return axios
.get(`https://api.escuelajs.co/api/v1/products/${id}`)
.then(r => r.data)
}
PS. react-query requires additional configuration ( context provider, config, etc ). Please look into docs on how to use it.

Data in React Component Not refreshing when Path/Location changes

I have a react app that has a "Bread Crumb Header" component, the data for this component comes from an API end point.
I use the bread crumb header component inside mulitiple components within the app, and based on the current path/window.location the bread crumb componet will get the data from the API and render the correct HTML via JSX.
The problem I have is when I navigate to diffent paths/window.location's within the application the bread crum component data doesn't update.
This is what the bread crumb component looks like:
import React, { useState, useEffect } from 'react';
import API from "../../API";
import { useLocation } from 'react-router-dom';
import { BreadCrumbTitleSection, SubtitleSection, Subtitle } from './breadCrumbHeaderStyle';
import { Breadcrumb } from 'react-bootstrap';
function BreadCrumbHeader() {
const location = useLocation();
const [breadCrumbData, setBreadCrumbData] = useState([]);
const getBreadCrumbData = async () => {
const breadCrumbHeaderResponse = await API.fetchBreadCrumbHeader(location.pathname);
setBreadCrumbData(breadCrumbHeaderResponse);
};
useEffect(() => {
getBreadCrumbData();
}, []);
return (
<div>
<BreadCrumbTitleSection backgroundUrl={breadCrumbData.BreadCrumbBgImage}>
<div className="container">
<div className="row no-gutters">
<div className="col-xs-12 col-xl-preffix-1 col-xl-11">
<h1 className="h3 text-white">{breadCrumbData.BreadCrumbTitle}</h1>
<Breadcrumb>
{breadCrumbData.BreadCrumbLinks.map(breadCrumbLink => (
<Breadcrumb.Item href={breadCrumbLink.LinkUrl} key={breadCrumbLink.Id} active={breadCrumbLink.IsActive}>
{breadCrumbLink.LinkText}
</Breadcrumb.Item>
))}
</Breadcrumb>
</div>
</div>
</div>
</BreadCrumbTitleSection>
<SubtitleSection>
<Subtitle> {breadCrumbData.SubTitle}</Subtitle>
</SubtitleSection>
</div>
);
}
export default BreadCrumbHeader;
and this is an example of how I am using it inside other components:
import React, { useContext } from 'react';
import { useParams } from "react-router-dom";
import { MenuContext } from '../context/menuContext';
import RenderCmsComponents from '../../components/RenderCmsComponents/';
import BreadCrumbHeader from '../../components/BreadCrumbHeader/';
import { CategorySection, CategoryContainer, CategoryItemCard, CategoryItemCardBody, CategoryItemCardImg, CategoryItemTitle, CategoryRow, AddToCartButton, ProductDescription} from './categoryStyle';
function Category() {
const [categoryItems] = useContext(MenuContext);
const { id } = useParams();
const category = categoryItems.find(element => element.CategoryName.toLowerCase() === id.toLowerCase());
var dynamicProps = [];
{
category && category.Products.map(productItem => (
dynamicProps.push(productItem.ProductOptions.reduce((acc, { OptionName, OptionsAsSnipCartString }, i) => ({
...acc,
[`data-item-custom${i + 1}-name`]: OptionName,
[`data-item-custom${i + 1}-options`]: OptionsAsSnipCartString
}), {}))));
}
return (
<div>
<BreadCrumbHeader /> << HERE IT IS
<CategorySection backgroundurl="/images/home-slide-4-1920x800.jpg" fluid>
<CategoryContainer>
<CategoryRow>
{category && category.Products.map((productItem, i) => (
<CategoryItemCard key={productItem.ProductId}>
<CategoryItemTitle>{productItem.ProductName}</CategoryItemTitle>
<CategoryItemCardBody>
<ProductDescription>{productItem.Description}</ProductDescription>
<div>
<CategoryItemCardImg src={productItem.ProductImageUrl} alt={productItem.ProductName} />
</div>
</CategoryItemCardBody>
<AddToCartButton
data-item-id={productItem.ProductId}
data-item-price={productItem.Price}
data-item-url={productItem.ProductUrl}
data-item-description={productItem.Description}
data-item-image={productItem.ProductImageUrl}
data-item-name={productItem.ProductName}
{...dynamicProps[i]}>
ADD TO CART {productItem.Price}
</AddToCartButton>
</CategoryItemCard>
))}
</CategoryRow>
</CategoryContainer>
</CategorySection>
<RenderCmsComponents />
</div>
);
}
export default Category;
I found this post on stack overflow:
Why useEffect doesn't run on window.location.pathname changes?
I think this may be the solution to what I need, but I don't fully understand the accepted answer.
Can someone breakdown to be how I can fix my issue and maybe give me an explaination and possible some reading I can do to really understand how hooks work and how to use them in my situation.
It seems that you should re-call getBreadCrumbData every time when location.pathname was changed. In the code below I've added location.pathname to useEffect dependency list
const location = useLocation();
const [breadCrumbData, setBreadCrumbData] = useState([]);
const getBreadCrumbData = async () => {
const breadCrumbHeaderResponse = await API.fetchBreadCrumbHeader(location.pathname);
setBreadCrumbData(breadCrumbHeaderResponse);
};
useEffect(() => {
getBreadCrumbData();
}, [location.pathname]); // <==== here

Why am I getting a null value in localStorage even after parsing it?

I'm trying to build a crypto tracker where you can add the items by clicking a button. Each time the button is clicked, the array should be added to the storage with the name "crypto" and then on another component where it is the portfolio one we should be able to get the items.
Here is where I set the item to an array whenever I click the add button:
import React, {useEffect, useState} from 'react'
import axios from 'axios'
import './tracker.css'
import Navigation from './Nav.js'
import {
BrowserRouter as Router,
Switch,
Route,
Link
} from "react-router-dom";
function Tracker() {
const [data, setData] = useState([])
const [portfolio, setPortfolio] = useState([])
useEffect(() => {
setInterval(() => {
const fetchData = async () => {
const result = await axios('https://api.coingecko.com/api/v3/coins/markets?vs_currency=usd&order=market_cap_desc&per_page=100&page=1&sparkline=false' , {
'mode': 'no-cors',
'headers': {
'Access-Control-Allow-Origin': '*',
}
})
setData(result.data)
}
fetchData()
}, 1000)
}, [])
return (
<div>
<Navigation />
<div className="tracker__names">
<b>Coins</b>
<b>Symbol</b>
<b>Price</b>
<b>Market Cap</b>
</div>
{data.map((coins, i) => {
const addToPortfolio = () => {
setPortfolio([...portfolio, data[i]])
localStorage.setItem('crpyto', JSON.stringify(portfolio))
}
return (
<>
<div className="tracker__main">
<div className="tracker__img">
<img src={coins.image} className="tracker__image"/>
<button key={i} onClick={addToPortfolio}>{coins.id}</button>
</div>
<div className="tracker__symbol">
<p>{coins.symbol}</p>
</div>
<div className="tracker__price">
<p></p>
${coins.current_price}
</div>
<div className="tracker__market">
<p></p>
${coins.market_cap}
</div>
</div>
</>
)
})}
</div>
)
}
export default Tracker
Here is the component where I want to get the item:
import React, {useState, useEffect} from 'react'
import Navigation from './Nav.js'
function Portfolio() {
const [value, setValue] = useState(JSON.parse(localStorage.getItem('crypto')) || '')
useEffect(() => {
console.log(value)
}, )
return (
<div>
<Navigation />
{value}
</div>
)
}
export default Portfolio
It is because useState is executed before JSON.parse(localStorage.getItem('crypto')) and once you get the value from the localstorage, component doesn't re-render.
Instead do:
useEffect(() => {
const crypto = JSON.parse(localStorage.getItem('crypto'))
if(crypto) setValue(crypto)
}, [])
In React you can't set a state var and on the next line save it in localStorage (or even read it). This because setPortfolio is async!
To solve this you have I think 2 ways:
store value and not state variable:
localStorage.setItem('crpyto', JSON.stringify([...portfolio, data[i]]))
use an useEffect hook:
useEffect(() => {
localStorage.setItem('crpyto', JSON.stringify(portfolio))
}, [portfolio])
First of all, when yo uare setting state like this, in the next block of code, portfolio won't necessarily have the updated state.
setPortfolio([...portfolio, data[i]])
localStorage.setItem('crpyto', JSON.stringify(portfolio))
update the portfolio like this.
const newPortfolio = [...portfolio, data[i]];
setPortfolio(newPortfolio )
localStorage.setItem('crpyto', JSON.stringify(newPortfolio))

Props not getting Rendered in NextJs

I have a post page in blog model, which includes Detail and Comment Component. getStaticProps from the post page gets the data, and I am passing this data as props to the Detail Component. Yet the the Detail component is not getting rendered.
Here's the post page:
import BlogDetail from "../../components/BlogDetail/BlogDetail"
import { CSSTransition } from 'react-transition-group'
import AuthContextProvider from "../../context/AuthContext"
import Cookie from "../../components/Cookie"
import { ThemeContext } from "../../context/ThemeContext"
import { useContext } from "react"
import '#fortawesome/fontawesome-svg-core/styles.css'
import dynamic from 'next/dynamic'
const Navbar = dynamic(() => import("../../components/Navbar"), { ssr: false })
import axios from "axios"
import { baseURL } from "../../functions/baseUrl"
export const getStaticPaths = async () => {
const res = await axios.get(baseURL + "/post/");
const info = await res.data
const paths = info.map(datum => {
return {
params: { slug: datum.slug }
}
})
return {
paths,
fallback: false
}
}
export const getStaticProps = async (context) => {
const slug = context.params.slug;
const res = await axios.get(baseURL + '/post/' + slug + "/");
const data = await res.data;
return {
props: { datum: data }
}
}
const Blog = (datum) => {
const [dark] = useContext(ThemeContext)
return (
<div className={`main ${dark}`}>
<AuthContextProvider>
<Navbar />
<CSSTransition
in={true}
classNames="pagetransitions"
timeout={100}
key={1}
appear={true}
unmountOnExit
>
<div>
<Cookie />
<BlogDetail title={datum.title} datum={datum} />
</div>
</CSSTransition>
</AuthContextProvider>
</div>
)
}
export default Blog;
And my BlogDetail model:
import React, { useState } from 'react';
import styles from "../../styles/blogDetail.module.css"
import timeformatter from "../../functions/timeFormatter"
import Tags from "../Tags";
import Head from "next/head"
import dynamic from 'next/dynamic'
const Favourite = dynamic(() => import("./Favourite"), { ssr: false })
const Comment = dynamic(() => import("./Comment"), { ssr: false })
function BlogDetail(props) {
const data = useState(props.datum)
function createMarkup() {
return { __html: data.text };
}
return (
<div className={styles.blog_text_container}>
<div>
<h1>{data.title}</h1>
<Tags tag={data.tags} />
{data.image_head === null ? (
<span></span>
) : (
<div className={styles.article_detail_image}>
<img className={styles.blog_header_image_detail} alt={data.alt_image_text} src={data.image_head}></img>
</div>
)}
<br></br>
<div dangerouslySetInnerHTML={createMarkup()} />
<br></br>
<span>{data.comments}</span>
<br></br>
<span>Published: {timeformatter(data.created_at)}</span>
<br></br><br></br>
<Favourite id={data.id} favcount={data.favcount} /><br></br>
<Comment id={data.id} /><br></br>
<br></br>
</div>
</div>
)
}
export default BlogDetail
I have tried passing my props individually like the titles, texts. But nodda. I have tried directly rendering the props without including state. Any help would appreciated.
In post page destructure dataum
...other code remains same
const Blog = ({datum}) => {
...other code remains same
In blogdetail page
...other code remains same
function BlogDetail({datum : data}) { // destructuring dataum and naming it as data since you have used data.* in your code
// you donot need useState here
...other code remains same
The issue is probably here
// some code
const Blog = (datum) => {
// some code
Make it to
const Blog = ({datum}) => {
// your code
As explained here
https://nextjs.org/docs/basic-features/data-fetching#simple-example

React shows unfinished elements before the page renders completely

I am making a posts project with React. Whenever My home page just consists a bunch of posts in cards view. If I click on a certain card, it should navigate me to that post with some details. However, before the page renders completely, I still see some lines or 'unfinished' elements so to speak.
This is what I see before the post and it's description render completely
How can I fix this?
Here is my JS file with posts:
import React, { Component } from 'react'
import { Card } from "react-bootstrap";
import { Link } from "react-router-dom";
import './Posts.css'
export class Posts extends Component {
render() {
return (
<div>
{this.props.posts.map(post => (
<Link to={`/post/${post._id}`} key={post._id}>
<Card key={post._id} className="shadow-sm">
<Card.Img variant="top" src={post.image} />
<Card.Body>
<Card.Title id="cardtitle">{post.title}</Card.Title>
</Card.Body>
</Card>
</Link>
))}
</div>
)
}
}
And here is the Post detail:
import React, { useState, useEffect } from 'react'
import axios from "axios";
import { Media } from "react-bootstrap";
import './Post.css'
function Post({ match }) {
const [post, setPost] = useState({});
useEffect(() => {
const fetchPost = async () => {
const res = await axios.get(`${POST_URL}${match.params.id}`);
setPost(res.data);
}
fetchPost();
// eslint-disable-next-line react-hooks/exhaustive-deps
}, []);
const POST_URL = `/api/v1/posts/`;
return (
<Media>
<img className="align-self-center mr-3 postImage" src={post.image} alt={post.title} />
<Media.Body>
<h5 className="postTitle text-center">{post.title}</h5>
<p>{post.description}</p>
</Media.Body>
</Media>
)
}
export default Post
You can create a function inside your component that conditionally render if the data has returned from the API. Something like this:
import React, { useState, useEffect } from 'react'
import axios from "axios";
import { Media } from "react-bootstrap";
import './Post.css'
function Post({ match }) {
const [post, setPost] = useState();
useEffect(() => {
const fetchPost = async () => {
const res = await axios.get(`${POST_URL}${match.params.id}`);
setPost(res.data);
}
fetchPost();
// eslint-disable-next-line react-hooks/exhaustive-deps
}, []);
const POST_URL = `/api/v1/posts/`;
const renderPost = () => {
if (post) {
return(
<Media>
<img className="align-self-center mr-3 postImage" src={post.image} alt={post.title} />
<Media.Body>
<h5 className="postTitle text-center">{post.title}</h5>
<p>{post.description}</p>
</Media.Body>
</Media>
);
}
return <h1>Loading</h1>;
}
return (
renderPost();
)
}
export default Post
I recommend you to render a spinner or a placeholder to improve the user experience while the data is loading.

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