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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...
#4: Post edited
Cannot read properties of undefined (reading 'map') error in mern stack project
- Cannot read properties of undefined (reading 'map') error in MERN stack project
#3: Post edited
- 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.please help recreate in your machine. thanks.
- 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?
- ```react
- //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.
#2: Post edited
- 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 } = useProductsQuery()- 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.please help recreate in your machine. thanks.
- 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.please help recreate in your machine. thanks.
#1: Initial revision
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 } = useProductsQuery() 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.please help recreate in your machine. thanks.