Printing JSON data in React JS through mapping

Question

I have this link https://api.covid19api.com/countries, which holds the "Country", "Slug", and "ISO2" of several countries. I want to display, only the "Country" value in tag.I wrote the following code


function App() {

  const [countries,setCountries] = React.useState();

  React.useEffect(()=>{
    async function fetchData(){
      const data = fetch('https://api.covid19api.com/countries').then(resp => resp.json());
      setCountries(data)
    }
    fetchData();
  },[])

  if(!countries){
    return(
      <h3>Loading.....</h3>
    )
  }

  return (
    <div>
        {
          countries.map(() => <h1>{countries.Country}</h1>)
        }
    </div>
  );
}

export default App;

but, it was giving the following error

TypeError: countries.map is not a function

Could anyone please say the correct way to do it

Probably because countries does not exist yet during rendering. Do something like countries && countries.ma(...). You can do a console.log just before the return at one point countries will be undefined then will later be defined after the API request is done. — kimobrian254
– kimobrian254, Commented Jun 6, 2020 at 19:07

ABGR · Accepted Answer · 2020-06-06 19:21:35Z

2

I think you're just missing an await before setCountries.

const data = await fetch('https://api.covid19api.com/countries').then(resp => resp.json());
      setCountries(data)

Also, I think, it's better to initialise countries with an empty array here in this case.

const [countries,setCountries] = React.useState([]);

edited Jun 6, 2020 at 19:21

answered Jun 6, 2020 at 19:14

ABGR

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1 Comment

charlietfl Over a year ago

That is only one of the problems. No default empty array is another as well as incorrect use of map()

Thanveer Shah · Accepted Answer · 2020-06-06 19:31:56Z

2

3 issues

1 => You are not using await

2 => You are not passing any parameter in the map method

3 => Response is an array, So you need to make your state an array.

Updated Code.

function App() {

  const [countries,setCountries] = React.useState([]);

  React.useEffect(()=>{
    async function fetchData(){
      const data = await fetch('https://api.covid19api.com/countries').then(resp => resp.json());
      setCountries(data)
    }
    fetchData();
  },[])

  if(!countries){
    return(
      <h3>Loading.....</h3>
    )
  }

  return (
    <div>
        {
          countries.map((data) => <h1>{data.Country}</h1>)
        }
    </div>
  );
}

export default App;

edited Jun 6, 2020 at 19:31

answered Jun 6, 2020 at 19:29

Thanveer Shah

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4 Comments

charlietfl Over a year ago

Third issue is countries is not an array on initial render. Modifying to React.useState([]); would set empty array as default

Thanveer Shah Over a year ago

You are right , I just checked the API. Let me fix that

charlietfl Over a year ago

@RahulDwivedi Setting empty array as default value for countries solves that

charlietfl Over a year ago

@RahulDwivedi I mean setting default using React.useState([]);. Syntax you used makes no sense

Amit Kumar · Accepted Answer · 2020-06-06 19:35:44Z

-1

You have had await keyword with async. The word 'async' before a function means one simple thing: a function always returns a promise and the keyword await makes JavaScript wait until that promise settles and returns its result. So it will be something like this

React.useEffect(() => {
    async function fetchData() {
      const data = await fetch("https://api.covid19api.com/countries").then(
        resp => resp.json()
      );
      setCountries(data);
    }
    fetchData();
  }, []);

This is my codesandbox link if wanna check - https://codesandbox.io/s/cocky-lewin-7wwn9

answered Jun 6, 2020 at 19:35

Amit Kumar

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