LocalStorage issue in React

Question

I have a save() function in my React app which saves data from a rest api into an empty array saved[]. But the problem is, when I refresh the page and click the Save button it overwrites the data in the array, I don't seem to see where the issue is? My code so far is:

import React, { Component } from 'react';
import './news-hero.css';
import Carousel from "react-multi-carousel";
import "react-multi-carousel/lib/styles.css";

const responsive = {
    superLargeDesktop: {
        breakpoint: { max: 4000, min: 3000 },
        items: 1,
    },
    desktop: {
        breakpoint: { max: 3000, min: 1024 },
        items: 1,
    },
    tablet: {
        breakpoint: { max: 1024, min: 464 },
        items: 1,
    },
    mobile: {
        breakpoint: { max: 464, min: 0 },
        items: 1,
    },
};

class NewsHero extends Component {
    state = {
        loading: false,
        data: [],
        headline: [],
        saved: []
    }

    saved = headline => {
        this.setState(
         (prevState) => ({ saved: [...prevState.saved, headline] }),
          () => {
            console.log('Saved articles = ', this.state.saved);
            alert('Article saved');
            localStorage.setItem('saved', JSON.stringify(this.state.saved));
            localStorage.getItem('saved');
          });
      }

    constructor(props) {
        super(props)
        this.saved = this.saved.bind(this)
    }

    onError() {
        this.setState({
            imageUrl: "../assets/img-error.jpg"
        })
    }

    componentDidMount() {
        this.setState({ loading: true })
        fetch('https://newsapi.org/v2/everything?q=timbaland&domains=rollingstone.com,billboard.com&excludeDomains=townsquare.media&apiKey=7')
            .then(headline => headline.json())
            .then(headline => this.setState({ headline: headline.articles, loading: false }, () => console.log(headline.articles)))
    }

    render() {

        return (
            <div className="hero">
                <h2 className="text-left">News</h2>

                {this.state.loading
                    ? "loading..."
                    : <div>
                        <Carousel
                            additionalTransfrom={0}
                            showDots={true}
                            arrows={true}
                            autoPlaySpeed={3000}
                            autoPlay={false}
                            centerMode={false}
                            className="carousel-hero"
                            containerClass="container-with-dots"
                            dotListClass="dots"
                            draggable
                            focusOnSelect={false}
                            infinite
                            itemClass="carousel-top"
                            keyBoardControl
                            minimumTouchDrag={80}
                            renderButtonGroupOutside={false}
                            renderDotsOutside
                            responsive={responsive}>
                            {this.state.headline.map((post, indx) => {
                                return (
                                    <div className="text-left mt-5" key={indx}>
                                        <img className="media-img card-img-top card-img-hero" src={post.urlToImage} alt="Alt text"></img>
                                        <div className="card-body container hero-text-body">
                                            <h1 className="card-title hero-title text-truncate">{post.title}</h1>
                                            <button className="btn-primary btn mt-2 mb-4" onClick={() => this.saved(post)}>Add this article</button>
                                            <p className="card-text">{post.description}</p>
                                            <a href={post.url} target="_blank" rel="noopener noreferrer">Read More</a>
                                        </div>
                                    </div>
                                )
                            })}
                            {this.state.saved.map((post, indx) => {
                                return (
                                    <div className="text-left mt-5" key={indx}>
                                        <img className="media-img card-img-top card-img-hero" src={post.urlToImage} alt="Alt text"></img>
                                        <div className="card-body container hero-text-body">
                                            <h1 className="card-title hero-title text-truncate">{post.title}</h1>
                                            <button className="btn-primary btn mt-2 mb-4" onClick={() => this.saved(post)}>Add this article</button>
                                            <p className="card-text">{post.description}</p>
                                            <a href={post.url} target="_blank" rel="noopener noreferrer">Read More</a>
                                        </div>
                                    </div>
                                )
                            })}
                        </Carousel>

                    </div>
                }
            </div>
        )
    }
}
export default NewsHero;

Answer 1

You need to get the state from local storage and update it, before writing it to local storage

constructor(props) {
    super(props)

    const saved = localStorage.getItem('saved');

    state = {
        loading: false,
        data: [],
        headline: [],
        saved: saved ? JSON.parse(saved) : []
    }

    this.saved = this.saved.bind(this)
}

Answer 2

I'm guessin it's because you aren't restoring the saved array from the Local Storage when mounting you'r component.

When you refresh the page your components lose their states and get mounted again.

Try adding:

    componentDidMount() {
        this.setState({ loading: true, saved: localStorage.getItem('saved') ? JSON.parse(localStorage.getItem('saved')) : [] })
        fetch('https://newsapi.org/v2/everything?q=timbaland&domains=rollingstone.com,billboard.com&excludeDomains=townsquare.media&apiKey=7')
            .then(headline => headline.json())
            .then(headline => this.setState({ headline: headline.articles, loading: false }, () => console.log(headline.articles)))
    }