undefined 不是 function （'...this.state.dataBanner.map...'附近）

Question

I have already checked some similar questions with the same problem: ReactJS TypeError: undefined is not a function (near '...this.state.data.map...')

I have followed each of the steps: dataBanner:[] and dataBanner:responseJson

...
import Swiper from 'react-native-swiper'
...
constructor(props){
    super(props);
    this.state = {
        dataNews:[],
        dataBanner:[]
    }
}
componentDidMount(){
    return fetch(baseUrl)
    .then((response)=> response.json())
    .then((responseJson)=>{
        console.log(responseJson)
        this.setState({
            dataNews:responseJson,
            dataBanner:responseJson
        })
        //console.log(responseJson)
    })
    .catch((error)=>{
        console.log(error)
    })
}

But the following code still gives me an error:

            <Swiper>
                {this.state.dataBanner.map((itemImg)=>{
                    return (
                        <Image
                            source ={{ uri: itemImg.urlToImage }}
                            style ={{height:"100%", width:"100%"}}
                        />
                    )
                })}
            </Swiper>

Answer 1

You can try

        this.setState({
            dataNews:responseJson?.articles, // add articals here
            dataBanner:responseJson?.articles // add articals here
        })
   

and also you can validate

<Swiper>
    {this.state.dataBanner?.length > 0 && this.state.dataBanner.map((itemImg) => {
        return (
            <Image
                source={{ uri: itemImg.urlToImage }}
                style={{ height: "100%", width: "100%" }}
            />
        )
    })}
</Swiper>