Reactjs 如何修复。TypeError:无法读取属性'；用户'；空的

我试图创建状态的副本，更新副本并将其分配回状态，但它抛出了一个错误

这是我的密码：

class App extends Component {
  constructor(){
    super()
    this.State = {
      user: {
        username: '',
        password: ''
      }
    }
  }
  updateuser = (attr, event) => {
    console.log(attr + '==' + event.target.value);
    let updateduser = Object.assign({}, this.state.user) // errored line
    updateduser[attr] = event.target.value

    this.setState({
      user: updateduser
    })
  }

控制台错误：

App.js:17 Uncaught TypeError: Cannot read property 'user' of null
    at App._this.updateuser (App.js:17)
    at HTMLUnknownElement.callCallback (react-dom.development.js:147)
    at Object.invokeGuardedCallbackDev (react-dom.development.js:196)
    at invokeGuardedCallback (react-dom.development.js:250)
    at invokeGuardedCallbackAndCatchFirstError (react-dom.development.js:265)

---

这只是一个输入错误，将this.State更改为this.State

class App extends Component {
  constructor(){
    super()
    this.state = { //fix
      user: {
        username: '',
        password: ''
      }
    }
  }

  updateuser = (attr, event) => {
    console.log(attr + '==' + event.target.value);
    let updateduser = Object.assign({}, this.state.user) // errored line
    updateduser[attr] = event.target.value

    this.setState({
      user: updateduser
    })
  }

---

只需将

this.State

更新为

this.State

谢谢你，praveen:）我是新的反应者，很乐意帮助你