ReactJS中的if else返回false。

huangapple
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英文:

ReactJS if else gives false

问题

I have reviewed the provided code. If you have any specific questions or need assistance with a particular part of the code, please feel free to ask.

英文:

i have button (for add item to localStorage) when i click "Add to favourites" adding item to localStorage and when i click again it deleting this item from localStorage, everything fine. But when i refresh page and click button it only adding, i mean refreshing clicking, refreshing clicking and it only adding it must be delete because i already added 1 time. And when i click two times without refreshing it deleting 1 item which i want 2-3 times(how many time i added with refresh). if gives me false every time with refresh, without refresh (clicking 2 times) then it gives me true. i think something wrong with if. Can someone help me please?


    import React, { useState } from 'react';
import { Button, Card } from 'react-bootstrap';
import { useThemeHook } from '../GlobalComponents/ThemeProvider';
import { useCart } from 'react-use-cart';
import { BsCartPlus } from 'react-icons/bs';
import { Link } from "@reach/router";
import { useInView } from 'react-intersection-observer';
import { MainContext, useContext } from '../context';


const ProductCard = (props) => {
    // const [state,setState]=useState({
    //     favourites:[]       
    //    });

    const { favourites, setFavourites} = useContext(MainContext);
  

    let { image, price, title, id } = props.data;
    const [theme] = useThemeHook();
    const { addItem } = useCart();

    const { ref: headerAni, inView: headerAniVisible } = useInView();

    const addToCart = () => {
        addItem(props.data);
    }
    const handleFavourites = (likedItem) => {
        let oldData = JSON.parse(localStorage.getItem('liked')) ?? []
        if (favourites.includes(likedItem.id)) {
            oldData = oldData.filter((m) => m.id !== likedItem.id)
            console.log("if", oldData)

        } else {
            oldData.push(likedItem)
            console.log("else", oldData)
        }
        localStorage.setItem("liked", JSON.stringify(oldData));
        console.log(oldData);
        handleFavouritesState();
    };
    const handleFavouritesState = () => {
        let oldData = JSON.parse(localStorage.getItem("liked")) ?? []
        let temp = oldData.map((likedItem) => likedItem.id);
        setFavourites([...temp])
        console.log("son", oldData)
    };

    return (
        <>

            <Card
                style={{ width: '18rem', height: 'auto' }}
                className={`${theme ? 'bg-light-black text-light' : 'bg-lihgt text-black'} text-center p-0 overflow-hidden shadow mx-auto mb-4`}

                ref={headerAni}
            >
                <Link to={`/product-details/${id}`}>
                    <div style={{
                        background: 'white', height: '15rem', overflow: 'hidden', display: 'flex',
                        justifyContent: 'center', alignItems: 'center', marginBottom: 'inherit'
                    }}>
                        <div style={{ width: '9rem' }}>
                            <Card.Img variant="top" src={image} className="img-fluid" data-aos-easing="ease-out-cubic"
                                data-aos-duration="3000" data-aos={`${headerAniVisible ? "" : "zoom-out"}`} />
                        </div>
                    </div>
                </Link>
                <Card.Body>
                    <Card.Title style={{ textOverflow: 'ellipsis', overflow: 'hidden', whiteSpace: 'nowrap' }}>
                        {title}
                    </Card.Title>
                    <Card.Title>
                        $ <del><span className="">{price * 2}</span></del>
                    </Card.Title>
                    <Card.Title>
                        $ <span className="h3">{price}</span>
                    </Card.Title>
                    <Button
                        onClick={() => addToCart()}
                        className={`${theme ? 'bg-dark-primary text-black' : 'bg-light-primary'} d-flex align-item-center m-auto border-0`}
                    >
                        <BsCartPlus size="1.8rem" />
                        Add to cart
                    </Button>
                    <Button
                        onClick={() => handleFavourites(props.data)}
                        className={`${theme ? 'bg-dark-primary text-black' : 'bg-light-primary'} d-flex align-item-center m-auto border-0`}
                    >
                        <BsCartPlus size="1.8rem" />
                        Add to Favourites
                    </Button>
                </Card.Body>
            </Card>
        </>
    );
};

export default ProductCard;

i get data from home component with props if it will be help you

import { useRef } from 'react';
import React, { useEffect, useState } from 'react';
import { Container, Row, Col, InputGroup, FormControl } from 'react-bootstrap';
import { useThemeHook } from '../GlobalComponents/ThemeProvider';
import { BiSearch } from 'react-icons/bi';
import SearchFilter from 'react-filter-search';
import ProductCard from '../components/ProductCard';
import Carousel from 'react-bootstrap/Carousel';
import ScrollAnimation from 'react-animate-on-scroll';
import { useInView } from 'react-intersection-observer';
const Home = () => {
const [theme] = useThemeHook();
const [searchInput, setSearchInput] = useState('');
const [productData, setProductData] = useState([]);
const { ref: myRef, inView: myElementIsVisible } = useInView();
const { ref: rocketRef, inView: rocketIsVisible } = useInView();
const { ref: bannerOne, inView: bannerOneVisible } = useInView();
const { ref: headerAni, inView: headerAniVisible } = useInView();
async function getResponse() {
const res = await fetch('https://fakestoreapi.com/products')
.then(res => res.json());
setProductData(await res);
}
useEffect(() => {
getResponse();
}, []);
const [sortState, setSortState] = useState("none");
const sortMethods = {
none: { method: (a, b) => null },
ascending: { method: (a, b) => (a.price - b.price) },
descending: { method: (a, b) => (a.title > b.title ? 1 : -1) },
};
return (
<>
<Carousel fade className='padd-1' data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${headerAniVisible ? "" : "fade-up"}`}>
<Carousel.Item ref={headerAni}>
<img
className="d-block w-100"
src="https://i.ibb.co/vwB9BV2/Untitled-design-33.png"
alt="First slide"
/>
<Carousel.Caption className='wid-300 pad-top' >
<h3>24/7 Texniki dəstək!</h3>
<p>
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. I
</p>
<a href='#' className='button'>More info</a>
</Carousel.Caption>
</Carousel.Item>
<Carousel.Item ref={headerAni}>
<img
className="d-block w-100"
src="https://i.ibb.co/PwrBm7q/Untitled-design-32.png"
alt="Second slide"
/>
<Carousel.Caption className='wid-300 pad-top' >
<h3>What is Lorem Ipsum?</h3>
<p>
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. I
</p>
<a href='#' className='button'>More info</a>
</Carousel.Caption>
</Carousel.Item>
<Carousel.Item ref={headerAni}>
<img
className="d-block w-100"
src="https://i.ibb.co/HYKM6z4/Untitled-design-34.png"
alt="Third slide"
/>
<Carousel.Caption className='wid-300 pad-top' >
<h3>What is Lorem Ipsum?</h3>
<p>
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. I
</p>
<a href='#' className='button'>More info</a>
</Carousel.Caption>
</Carousel.Item>
</Carousel>
<section className='home-wrapper-1 py-5'  >
<div className='container-xxl padd'  >
<div className='row' >
<div className='col-6'>
<div className='main-banner position-relative' ref={rocketRef}>
<img
src='https://i.ibb.co/PZtF0RM/main-banner-1.jpg'
className='img-fluid rounded-3'
alt='banner'
data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${rocketIsVisible ? "" : "fade-right"}`}
/>
<div className='main-banner-content position-absolute' data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${rocketIsVisible ? "" : "fade-right"}`}>
<h4>SUPERCHARGED FOR PODS</h4>
<h5>iPad S13+ Pro</h5>
<p>From $999.00 or $41.62/mo.</p>
<a href='#' className='button'>BUY NOW</a>
</div>
</div>
</div>
<div className='col-6'>
<div className='d-flex flex-wrap gap justify-content-between align-items-center'>
<div className='small-banner position-relative' ref={rocketRef}>
<img
src='https://i.ibb.co/HrZjrXC/catbanner-01.jpg'
className='img-fluid rounded-3'
alt='banner'
data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${rocketIsVisible ? "" : "fade-down"}`}
/>
<div className='small-banner-content position-absolute' data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${rocketIsVisible ? "" : "fade-down"}`}>
<h4>Best Sale</h4>
<h5>iPad S13+ Pro</h5>
<p>From $999.00 <br /> or $41.62/mo.</p>
</div>
</div>
<div className='small-banner position-relative' ref={rocketRef}>
<img
src='https://i.ibb.co/34Zk6Jv/catbanner-02.jpg'
className='img-fluid rounded-3'
alt='banner'
data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${rocketIsVisible ? "" : "fade-down"}`}
/>
<div className='small-banner-content position-absolute' data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${rocketIsVisible ? "" : "fade-down"}`}>
<h4>NEW ARRIVAL</h4>
<h5>Buy IPad Air</h5>
<p>From $999.00 <br /> or $41.62/mo.</p>
</div>
</div>
<div className='small-banner position-relative' ref={bannerOne}>
<img
src='https://i.ibb.co/5F9BZfw/catbanner-03.jpg'
className='img-fluid rounded-3'
alt='banner'
data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${bannerOneVisible ? "" : "fade-up"}`}
/>
<div className='small-banner-content position-absolute' data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${bannerOneVisible ? "" : "fade-up"}`}>
<h4>NEW ARRIVAL</h4>
<h5>Buy IPad Air</h5>
<p>From $999.00 <br /> or $41.62/mo.</p>
</div>
</div>
<div className='small-banner position-relative' ref={bannerOne}>
<img
src='https://i.ibb.co/pynHmdz/catbanner-04.jpg'
className='img-fluid rounded-3'
alt='banner'
data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${bannerOneVisible ? "" : "fade-up"}`}
/>
<div className='small-banner-content position-absolute' data-aos-easing="ease-out-cubic"
data-aos-duration="2000" data-aos={`${bannerOneVisible ? "" : "fade-up"}`}>
<h4>NEW ARRIVAL</h4>
<h5>Buy IPad Air</h5>
<p>From $999.00 <br /> or $41.62/mo.</p>
</div>
</div>
</div>
</div>
</div>
</div>
</section>
<Container className="py-4">
<Row className="justify-content-center">
<Col xs={10} md={7} lg={6} xl={4} className="mb-3 mx-auto text-center">
<h1 className={theme ? 'text-light my-5' : 'text-black my-5'}>Search products</h1>
<InputGroup className="mb-3">
<InputGroup.Text className={theme ? 'bg-black text-dark-primary' : 'bg-light text-light-primary'}>
<BiSearch size="2rem" />
</InputGroup.Text>
<FormControl
placeholder="Search"
value={searchInput}
onChange={(e) => setSearchInput(e.target.value)}
className={theme ? 'bg-light-black text-light' : 'bg-light text-black'}
/>
</InputGroup>
</Col>
<div style={{ width: '100%', display: 'flex', justifyContent: 'center' }} className='mb-3'>
<select style={{ width: '100px' }} defaultValue={'none'} onChange={(e) => setSortState(e.target.value)}>
<option value="none">None</option>
<option value="ascending">Price</option>
<option value="descending">A-Z</option>
</select>
</div>
<SearchFilter
value={searchInput}
data={productData}
renderResults={results => (
<Row className="justify-content-center">
{results?.sort(sortMethods[sortState].method).map((item, i) => (
<ProductCard data={item} key={i} />
))}
</Row>
)}
/>
</Row>
</Container>
</>
);
};
export default Home;

答案1

得分: 0

It seems that the issue is with the logic of the "handleFavourites" function.

const handleFavourites = (likedItem) => {
    let oldData = JSON.parse(localStorage.getItem('liked')) ?? [];
    if (favourites.includes(likedItem.id)) {
        oldData = oldData.filter((m) => m.id !== likedItem.id);
        console.log("if", oldData);
    } else {
        oldData.push(likedItem);
        console.log("else", oldData);
    }
    localStorage.setItem("liked", JSON.stringify(oldData));
    console.log(oldData);
    handleFavouritesState();
};

Checking if the oldData retrieved from the localStorage includes the id of the likedItem.

if (oldData.some((item) => item.id === likedItem.id)) {
    oldData = oldData.filter((m) => m.id !== likedItem.id);
    console.log("if", oldData);
} else {
    oldData.push(likedItem);
    console.log("else", oldData);
}
英文:

It seems that the issue is with the logic of the "handleFavourites"

const handleFavourites = (likedItem) => {
let oldData = JSON.parse(localStorage.getItem('liked')) ?? []
if (favourites.includes(likedItem.id)) {
oldData = oldData.filter((m) => m.id !== likedItem.id)
console.log("if", oldData)
} else {
oldData.push(likedItem)
console.log("else", oldData)
}
localStorage.setItem("liked", JSON.stringify(oldData));
console.log(oldData);
handleFavouritesState();

};

checking if the oldData retrieved from the localStorage includes the id of the likedItem

if (oldData.some((item) => item.id === likedItem.id)) {
oldData = oldData.filter((m) => m.id !== likedItem.id)
console.log("if", oldData)
} else {
oldData.push(likedItem)
console.log("else", oldData)

}

huangapple
  • 本文由 发表于 2023年4月13日 19:42:05
  • 转载请务必保留本文链接：https://go.coder-hub.com/76005005.html
  • css
  • html
  • javascript
  • jquery
  • reactjs
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