24 |     lastname: lname
  25 |   };
  26 |  
> 27 |   setobj(obj.data.push(dat));
     |                  ^
  28 |   console.log(obj);
  29 | };
  30 | 

i did not getting for the first time but when I again write the form value and submit it shows me this issues. down there is my full code.

function App() {
  
  var [obj, setobj] = useState({
    data: [
      {
        name: "chetan",
        lastname: "vashisht"
      }
    ]
  });

  var [name, setname] = useState("");
  var [lname, setlname] = useState("");

  const handle = (e) => {
    e.preventDefault();
    const dat = {
      name: name,
      lastname: lname
    };
   
    setobj(obj.data.push(dat));
    console.log(obj);
  };

  return (
    <div className="App">
      <form onSubmit={handle}>
        <label>Enter your name:</label>
        <input
          id="ing"
          type="text"
          value={name}
          onChange={(e) => setname(e.target.value)}
          required
          autoFocus
        />
        <br />
        <label>Enter last name:</label>
        <input
          type="text"
          value={lname}
          onChange={(e) => setlname(e.target.value)}
          required
        />
        <br />
        <button>Sign in</button>
      </form>
    </div>
  );
}

here I made an state which is the object using useState() where i have to store the data in the obj.data so I used the .push() method for storing the data . it works fine at first but then if i store values again it shows me error.