Cannot read properties of undefined (reading 'map') error in MERN stack project

In my project, I try to fetch data from the backend to display in the frontend using fetch API. Each time I do this I get Cannot read properties of undefined (reading 'map') error. When I check the console, I get a fulfilled promise.

I console.log the setState function to see what data is logged there but it returned undefined. why is my setState undefined?

In my backend, data displays fine when I test on thunder client in vscode. I also paste http://localhost:8080/data' in chrome and it also works.

why is data undefined?

//parent component
const Shopstore =  ()  => {


 const [dataProducts, setData ] = useState([])
 
  const url = 'http://localhost:8080/data'


  useEffect(()=> {

  const fetchfunc = async ()=> {
     try {
      const response = await fetch(url)
   
      if(!response.ok){
         throw new Error("network issues pls wait ");  
      }
      const data = await response.json()
       //this console.log returns a fulfilled promise
       console.log(data)

    //this console.log part returns undefined
     console.log( setData( data.dataProducts ));
       


     } catch (error) {
      console.log('error', error)
     }
  }
    

   fetchfunc()

  }, [] )

  


  return (
   
      <div className='Shopstore mt-5'>

      <Container>
      <Row>
     

      <Col md={10} className='big mt-3'>
          
       
          
           { dataProducts ? dataProducts.map((product)=> {
               return(
               <Listings key={product._id } { ... product } />
             
               )
           })  : <p>no data</p> }

          
            
          </Col>
      </Row>
     </Container>
      </div>
  )
}

export default Shopstore



//child component
const Listings = (products) => {

    const {  image, heading, price, _id  } = products

  return (

    <div className='listings mt-3 mb-3'>
        <Container>
         <Row>
         <Col md={4} id = { _id }>
         <div className="card mx-auto" style={{width: '250px'}}>
         
             <Card>
            <div className='image mx-auto '>
           <Link to={ `/shop/${products._id}` }> <img src={image} alt="" className='img-fluid' style={{width: '300px'}} /> </Link>
           <CardBody>
            <div className='title'>
              <h5>{heading}</h5>
            </div>
            <div className='price'>
              <span>{price}</span>
            </div>

            <div className=' mx-auto' >
            <button className='mx-auto cartbutton'  >Add to cart</button>
             </div>

           </CardBody>
            </div>
          </Card>    
         </div>
         </Col>
         </Row>
        </Container>
      
    </div>
  )
}

export default Listings

The ternary operator triggers no data as there is no data to display.

posted about 2 months ago

CC BY-SA 4.0

2mo ago by Alexei‭

emmaluga‭

1 reputation 1 0 0 1