React + TSのformのonSubmitで値を取得

サンプルコード

const onSubmit = (ev: React.FormEvent<HTMLFormElement>) => {
  ev.preventDefault();
  const target = ev.target as typeof ev.target & {
    t1: { value: string };
    t2: { value: string };
  };
  console.log(target.t1.value);
  console.log(target.t2.value);
};
return (
  <div className="App">
    <form onSubmit={(ev) => onSubmit(ev)}>
      <input type="text" id="t1" />
      <input type="text" id="t2" />
      <input type="submit" />
    </form>
  </div>
);

参考

• Forms and Events | React TypeScript Cheatsheets