Why array find returns nothing? using context and params

Question

Why array find returns nothing? using context and params

41 views Asked by Fatemeh Abtahi At 31 March 2024 at 14:38

i have this page component for each product information:

export default function Product() {
  const { data } = useContext(ShopContext);
  const { id } = useParams();
  
  if (!data) {
    return <div>Loading product...</div>;
  }

  const product = data.find((item) => item.id === id);

  return (
    <div>
      {product.title}
    </div>
  );
}

somehow product is undefined though data and id can be logged into console and their value is available, i made sure of it like this:

export default function Product() {
    const { data } = useContext(ShopContext);
    const { id } = useParams();

    if (!data) {
      return <div>Loading product...</div>;
    }

    const product = data.find((item) => item.id === id);
    
    return (
    <div>
      <div>{id}</div>        {/*this div is displayed as expected*/}
      <div>                  {/*this div is displayed as expected*/}
        {data.map((item) => (
          <div key={item.id}>{item.title}</div>
        ))}
      </div>
      <div>{product?.title}</div>       {/*this div is empty*/}
    </div>
  );
  }

for additional information i'm fetching the data from fakestoreapi.com in the app component and it works fine in other components. here's the fetching piece:

useEffect(() => {
    async function FetchData() {
      try {
        const response = await fetch("https://fakestoreapi.com/products");
        if (!response.ok) {
          throw new Error(`HTTP error: Status ${response.status}`);
        }
        let postsData = await response.json();
        postsData.sort((a, b) => {
          const nameA = a.title.toLowerCase();
          const nameB = b.title.toLowerCase();
          return nameA.localeCompare(nameB);
        });
        setData(postsData);
        setError(null);
      } catch (err) {
        setData(null);
        setError(err.message);
      } finally {
        setLoading(false);
      }
    }

    FetchData();
  }, []);

this is the context:


import { createContext } from "react";

export const ShopContext = createContext({
  data: [],
  loading: true,
  error: "",
  setData: () => {},
  cart: [],
  addToCart: () => {},
  removeFromCart: () => {},
});

and this is its states in app component:

const [data, setData] = useState(null);
const [loading, setLoading] = useState(true);
const [error, setError] = useState(null);
const [cart, setCart] = useState([]);

const addToCart = (productId) => {
  ....
};

const removeFromCart = (productId) => {
  .....
};

return (
    <ShopContext.Provider
      value={{
        data,
        loading,
        error,
        setData,
        cart,
        addToCart,
        removeFromCart,
      }}
    >
      <Header />
      <Body />
      <Footer />
    </ShopContext.Provider>
  );

okay i figured out that i was using === and ids had different types. i'm stupid yay


  const product = data.find((item) => item.id === Number(id));

Original Q&A

There are 1 answers

**YATIN GUPTA** · Answer 1 · 2024-03-31T15:33:26+00:00

I have replicated some part of code to illustrate you what mistake your are doing and how you can correct it.

context.jsx

import {createContext, useState} from 'react';

export const ShopContext = createContext();
const ShopProvider =  ({ children }) => {
  const [data, setData] = useState([]);

  const defaultContext = {
    data,
    setData,
  };

  return (
    <ShopContext.Provider value={defaultContext}>
      {children}
    </ShopContext.Provider>
  );
};
export default ShopProvider;

index.jsx

import React from 'react';
import ReactDOM from 'react-dom/client';
import ShopProvider from './context';

import { App } from './App.jsx'

ReactDOM.createRoot( 
  document.querySelector('#root')
).render(<ShopProvider><App /></ShopProvider>)

App.jsx

import React, {useContext, useEffect } from 'react';
import {ShopContext} from './context';
import Product from './Product';

export function App(props) {
  const {setData} = useContext(ShopContext); // So you require to get setter method from context.
  useEffect(() => {
    async function FetchData() {
      try {
        const response = await fetch("https://fakestoreapi.com/products");
        if (!response.ok) {
          throw new Error(`HTTP error: Status ${response.status}`);
        }
        let postsData = await response.json();
        postsData.sort((a, b) => {
          const nameA = a.title.toLowerCase();
          const nameB = b.title.toLowerCase();
          return nameA.localeCompare(nameB);
        });
        setData(postsData);
      } catch (err) {
        setData([]);
      }
    }
    FetchData();
  }, []);
  return (
      <div className='App'>
        <Product />
      </div>
  );
}

Product.jsx

import {useContext} from 'react';
import {ShopContext} from './context';

export default function Product() {
  const { data } = useContext(ShopContext);
  const id = 1;
  
  if (!data) {
    return <div>Loading product...</div>;
  }

  const product = data.find((item) => item?.id === id);

  return (
    <div>
      {product?.title}
    </div>
  );
}

Let me know if you face any problem in understanding this illustration.

TechQA.

Why array find returns nothing? using context and params

There are 1 answers

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