I have the following code in the ponent: I am not able to get an updated state.

When I call createUserList I can see the users in UserList ponent but in UserComponet when I log users I can not see users there.

But I can see updated state in react dev tools

The code I am using :

function UserComponent() {
    const [users, setUsers] = useState<any>([])


  const register = () => {
    userAgent.delegate = {
      onMessage(message: Message) {
        let usernameList = message.event.entry
        if (message.event['@_category'] === 'activate') {
          createUserList(usernameList); 
        } else if (message.event['@_category'] === 'de-activate') {
          
          // empty user list but I can see users in react dev tools
          console.log(users)
          const username = message.event.entry
          removeUser(username)
        }
      }
    }
  }

  const createUserList = (usernameList: any) => {
    let userList: any = []
    usernameList.forEach((user: any) => {
      userList.push({'uri': user['@_uri'], 'name': user['@_uri'].substr(10, 8)})
    })

    // here I can see updated userList
    console.log(userList)
    setUsers(userList)
    setTimeout(() => {

      // users is empty here
      console.log(users)
    }, 5000)
  }

  return (
    <UserList users={users}/>
  )

}

function UserList({users}) {
    return (
        <div>
            {users.map((user) => <h2>user</h2>)}
        </div>
    )
}

I have the following code in the ponent: I am not able to get an updated state.

When I call createUserList I can see the users in UserList ponent but in UserComponet when I log users I can not see users there.

But I can see updated state in react dev tools

The code I am using :

function UserComponent() {
    const [users, setUsers] = useState<any>([])


  const register = () => {
    userAgent.delegate = {
      onMessage(message: Message) {
        let usernameList = message.event.entry
        if (message.event['@_category'] === 'activate') {
          createUserList(usernameList); 
        } else if (message.event['@_category'] === 'de-activate') {
          
          // empty user list but I can see users in react dev tools
          console.log(users)
          const username = message.event.entry
          removeUser(username)
        }
      }
    }
  }

  const createUserList = (usernameList: any) => {
    let userList: any = []
    usernameList.forEach((user: any) => {
      userList.push({'uri': user['@_uri'], 'name': user['@_uri'].substr(10, 8)})
    })

    // here I can see updated userList
    console.log(userList)
    setUsers(userList)
    setTimeout(() => {

      // users is empty here
      console.log(users)
    }, 5000)
  }

  return (
    <UserList users={users}/>
  )

}

function UserList({users}) {
    return (
        <div>
            {users.map((user) => <h2>user</h2>)}
        </div>
    )
}

• javascript
• reactjs
• typescript
• use-state

3 Answers 3

You can use useEffect for that and pass the state as dependency, so every time users state get change it would get invoke.

useEffect(() => {
    console.log(users);
    }, [users])

useEffect should serve your purpose.

useEffect(() => {
console.log(users)
  
},[users]);

The above function (in this case, its console logging "users") is executed only when its (users) state is changed or updated. Consider replacing the setTimeOut with useEffect instead.

Use useEffect hook:

useEffect(() => console.log(users), [users])

Full code:

function UserComponent() {
  const [users, setUsers] = useState<any>([])

  useEffect(() => console.log(users), [users])


  const register = () => {
    userAgent.delegate = {
      onMessage(message: Message) {
        let usernameList = message.event.entry
        if (message.event['@_category'] === 'activate') {
          createUserList(usernameList); 
        } else if (message.event['@_category'] === 'de-activate') {
          
          // empty user list but I can see users in react dev tools
          console.log(users)
          const username = message.event.entry
          removeUser(username)
        }
      }
    }
  }

  const createUserList = (usernameList: any) => {
    let userList: any = []
    usernameList.forEach((user: any) => {
      userList.push({'uri': user['@_uri'], 'name': user['@_uri'].substr(10, 8)})
    })

    // here I can see updated userList
    console.log(userList)
    setUsers(userList)
  }

  return (
    <UserList users={users}/>
  )