react jsx的问题

Question

一、如下：在三玩表达式里使用map遍历导致报错
const { staffList } = this.state


二、这样就不会报错
const { staffList } = this.state
let obj = staffList[0]

Answer 1

写了一个例子 是可以的 没有报错 估计是代码问题

function App() {
  const [state, dispatch] = useReducer(reducer, initialState);
  const arr = [1, 2, 3, 4];
  return (
    <>
      Count: {state.count}
      <button onClick={() => dispatch({ type: "decrement" })}>-</button>
      <button onClick={() => dispatch({ type: "increment" })}>+</button>
      {arr.length ? (
        arr.map(item => <div key={item}>{item}</div>)
      ) : (
        <div>ssss</div>
      )}
    </>
  );
}

export default App;