react hooks - Unable to render data in Reactjs

Question

I am new to react and have been debugging this from yesterday and I finally decide to post as I am clueless of what is happening.

The following react code fetches data from the api and then renders it on the UI. But, there are few strange things happening here.

I get error saying as TypeError: Cannot read property 'map' of undefined initially but when I comment out {renderTableData(data)}& save and then again uncomment & save, the data is rendering perfectly on the UI

I am thinking that before even the data gets fetched from API, it is getting passed to the function renderTableData which is why in the console undefined is printed.

Here is the code

export default function TenantList(){
  const [data, setData] = useState([]);
    useEffect(() => {
      fetch('https://jsonplaceholder.typicode.com/users').then((response)=>{
        return response.json();
      }).then((data)=>{
        setData(data)
      })
    },[]);
 
function renderTableData(data) {
  console.log("hello ", data)
  return data.map((student, index) => {
      const { name, email } = student //destructuring
      return (
          <tr key={name}>
              <td>{name}</td>
              <td>{email}</td>
          </tr>
      )
  })
}
  return (
    <>
      <div>
        {renderTableData(data)}
      </div>
    </>
  )
}

Please suggest a workaround

Answer 1

You only want to run this function if you have the data, so check for it:

{data && renderTableData(data)}