错误:设置嵌套对象的值时，不能设置未定义的属性

Question

我想将errors的值设置为

{
email: {
primary:"[e-mail]"
}
}

编译后，返回一个错误:

Cannot set properties of undefined (setting 'primary')

App.js

import "./styles.css";
import { useState, useEffect } from "react";
export default function App() {
const [errors, setErrors] = useState({});
useEffect(() => {
const newErrors = errors;
newErrors.email.primary = "[e-mail]";
}, []);
return (
<div className="App">
<h1>Hello CodeSandbox</h1>
<h2>Start editing to see some magic happen!</h2>
</div>
);
}

Codesandbox: https://codesandbox.io/s/immutable-http-w0mue?file=/src/App.js

Answer 1

因为newErrors.email是undefined。就像这样更新:

newErrors.email = { primary: "[e-mail]" };