Required type to be defined for useState in typescript

Question

what is the required type to be defined for dataList in typescript please refer below snippet

const [dataList, setDataList] = useState([]); 
      dataList= [
                 [{header:"first",tail:"three"},{header:"second",tail:"four"}], 
                 [{header:"first",tail:"three"},{header:"second",tail:"four"}] 
                ];

Answer 1

You will need to provide the types for the dataList state, as TypeScript is unable to infer it. This can be done via interfaces or type alias.

interface Data {
  header: string;
  tail: string; 
}

And this is how you can use it on the useState generic parameter, whereby dataList is a multidimensional array of the Data interface that is defined above:

const [dataList, setDataList] = useState<Data[][]>([]);