Building an Auto Logout Session Timeout with React using hooks.

Sometimes, a user logs in to your application and forgets to logout. Let’s assume there are lots of sensitive information about the user on your application e.g personal information or transactions data. This leaves the user data vulnerable.

As a developer, you are to develop a solution that detects user inactiveness on your application. This solution is to help logout users whenever they are not making use of the application.

In this tutorial, we’re going to build the frontend using react and its hooks. Following the steps should give you a better understanding when working on either Vue or Angular.

Let’s get started!

Before we continue, please note that this tutorial assumes you have a basic understanding of react and react hooks. If not, kindly find available resources that’ll guide you through and come back here.

First, Let’s start by creating a javascript file in your component folder e.g SessionTimeout.js

To make things faster for us, let’s import all the things we need for the tutorial. You’ll need to install moment.

npm install moment --save

import React, {
  useState,
  useEffect,
  useCallback,
  useRef,
  Fragment,
} from "react"
import moment from "moment"

const SessionTimeout = () => {
  return <Fragment />
}

export default SessionTimeout

useState: accepts the initial value of the state item and returns an array containing the state variable, and the function you call to alter the state.

useCallback: This hook is useful when you have a component with a child frequently re-rendering.

useEffect: The function runs when the component is first rendered, and on every subsequent re-render/update.

useRef: This hook allows us to access a DOM element imperatively.

Fragment: This lets you group a list of children without adding extra nodes to the DOM.

Next, we list out all the state needed.

const SessionTimeout = () => {
  const [events, setEvents] = useState(['click', 'load', 'scroll']);
  const [second, setSecond] = useState(0);

events: This state helps to define our event listeners. You can add as many listeners as you want.

second: This state helps to define the remaining seconds left before the user will be logout.

Next, let’s write a function that initializes the timer when the component mounts.

const SessionTimeout = () => {
  const [events, setEvents] = useState(['click', 'load', 'scroll']);
  const [second, setSecond] = useState(0);

  // reset interval timer
  let resetTimer = useCallback(() => {

    if (isAuthenticated) {
      timeStamp = moment();
      sessionStorage.setItem('lastTimeStamp', timeStamp);
    } else {
      sessionStorage.removeItem('lastTimeStamp');
    }
  }, [isAuthenticated]);

  // Life cycle hook
  useEffect(() => {
    events.forEach((event) => {
      window.addEventListener(event, resetTimer);
    });

  }, [resetTimer]);

resetTimer: First, we check if the user is authenticated. If yes, we set the timestamp in sessionStorage and if not authenticated, we remove the timestamp from storage. The usecallback hook is used to look-up changes in user authentication.

In our useEffect hook, we then pass the function in our window.addEventListener.

Next, let’s also write a setTimeout function that checks for our stored timeStamp.

const SessionTimeout = () => {
  const [events, setEvents] = useState(['click', 'load', 'scroll']);
  const [second, setSecond] = useState(0);

  let timeStamp;
  let warningInactiveInterval = useRef();
  let startTimerInterval = useRef();

  // start inactive check
  let timeChecker = () => {
    startTimerInterval.current = setTimeout(() => {
      let storedTimeStamp = sessionStorage.getItem('lastTimeStamp');
      warningInactive(storedTimeStamp);
    }, 60000);
  };

timeChecker: We use this function to initialize the timer. The setTimeout method sets a timer that executes a function once the timer expires at 1 minute. We get the stored timeStamp from sessionStorage which is then sent to our warning function. We’ll look at the warningInactive function in a bit.

Next, let us run the timeChecker function

let timeStamp
let warningInactiveInterval = useRef()
let startTimerInterval = useRef()

// start inactive check
let timeChecker = () => {
  startTimerInterval.current = setTimeout(() => {
    let storedTimeStamp = sessionStorage.getItem("lastTimeStamp")
    warningInactive(storedTimeStamp)
  }, 60000)
}

// reset interval timer
let resetTimer = useCallback(() => {
  clearTimeout(startTimerInterval.current)

  if (isAuthenticated) {
    timeStamp = moment()
    sessionStorage.setItem("lastTimeStamp", timeStamp)
  } else {
    sessionStorage.removeItem("lastTimeStamp")
  }

  timeChecker()
}, [isAuthenticated])

// Life cycle hook
useEffect(() => {
  events.forEach(event => {
    window.addEventListener(event, resetTimer)
  })
  // Run the timeChecker
  timeChecker()
}, [resetTimer])

As you can see, the ideal timer is gradually coming to life. Here are the updates:

1. We run the timeChecker on both useEffect and resetTimer. This is because we want the timeChecker to do a check when the component mounts and when there’s a listened event on the window.
2. We also clear the setTimeout at the resetTimer function. This will help us stop any continuous loop.

Now that we’ve been able to write a time checker, let us write a function that warns the user.

let timeStamp
let warningInactiveInterval = useRef()
let startTimerInterval = useRef()

// start inactive check
let timeChecker = () => {
  startTimerInterval.current = setTimeout(() => {
    let storedTimeStamp = sessionStorage.getItem("lastTimeStamp")
    warningInactive(storedTimeStamp)
  }, 60000)
}

// warning timer
let warningInactive = timeString => {
  clearTimeout(startTimerInterval.current)

  warningInactiveInterval.current = setInterval(() => {
    const maxTime = 2 // Maximum ideal time given before logout
    const popTime = 1 // remaining time (notification) left to logout.

    const diff = moment.duration(moment().diff(moment(timeString)))
    const minPast = diff.minutes()
    const leftSecond = 60 - diff.seconds()

    if (minPast === popTime) {
      setSecond(leftSecond)
    }

    if (minPast === maxTime) {
      clearInterval(warningInactiveInterval.current)
      sessionStorage.removeItem("lastTimeStamp")
      // your logout function here
    }
  }, 1000)
}

Okay, don’t be scared. I know this is a bunch of code. I’ll explain everything.

warningInactive: Before doing anything in this function, let us first clear the setTimeout. Now, we can work with the setInterval method. The setInterval method is set to run repeatedly at every 1 second. And here, all thanks to momentjs, we can easily check for the time difference with it.

Click these links if you’re yet to understand the difference between setTimeout and setInterval.

We check the time difference between the current time and the stored time. minPast as minute past and leftSecond for counting down seconds.

Things to notes at this point:

1. The max ideal time is 2 minutes and popTime (which is the notification time) is set to 1 minute of user ideal.
2. We set the second to start counting once the minPast is equal to the popTime.
3. You can change the maxTime to increase the ideal timer for the user.
4. Lastly, we clear both the setInterval and sessionStorage once the minPast is equal with maxTime I.e once it’s 2 minutes of user ideal.

Yeah, that’s a lot of code we’ve written. Anyway, we’re almost done.

Lastly, let us go back to our resetTimer function and do some cleanups.

// reset interval timer
let resetTimer = useCallback(() => {
  clearTimeout(startTimerInterval.current)
  clearInterval(warningInactiveInterval.current)

  if (isAuthenticated) {
    timeStamp = moment()
    sessionStorage.setItem("lastTimeStamp", timeStamp)
  } else {
    clearInterval(warningInactiveInterval.current)
    sessionStorage.removeItem("lastTimeStamp")
  }
  timeChecker()
}, [isAuthenticated])

useEffect(() => {
  events.forEach(event => {
    window.addEventListener(event, resetTimer)
  })

  timeChecker()

  return () => {
    clearTimeout(startTimerInterval.current)
  }
}, [resetTimer, events, timeChecker])

Here are a few things we did:

1. We added a clearInterval method at the resetTimer. This is necessary to avoid unwanted loops. And also clear all running conditions when the user is not authenticated.
2. We also added a cleanup once the component unmount.

Finally! That’s all for everything. Now, we can test our code by adding the SessionTimeout.js in app.js or where you feel you’ll be needing it.

To spice things up, you can change the fragment to a modal that notifies the user of the warning. And you can also apply this with other frameworks.

The complete code for this tutorial can be found at https://github.com/sadewole/Idle-session-timer. And thanks to Flavio Copes, I used his definition of hooks.

--

You can like and do leave a comment for any contribution to this article on medium. Thank you.