state = { items: Array.from({ length: 20 }) }; to useState code example

Example: functional component how to add to existing array react

const {useState, useCallback} = React;
function Example() {
    const [theArray, setTheArray] = useState([]);
    const addEntryClick = () => {
        setTheArray([...theArray, `Entry ${theArray.length}`]);
    };
    return [
        ,
        
{theArray.map(entry =>
          
{entry}
        )}
        
    ];
}

ReactDOM.render(
    ,
    document.getElementById("root")
);