How can you verify if a JWT is still valid?

An elegant solution to handle token expiration is when you set the token(in LocalStorage or store(redux), or both) is also to have an Async function that runs exactly when the token expires. Something like this:

const logUserOut = token =>{
    setTimeout(()=> MyLogoutFunction(), token.expiresIn)
}

This way you make sure that the user won't be logged when the token is no longer valid.

You can have your client side decode the JWT and check an expiry field and compare it with system time.

eg.

  isExpired: (token) => {
    if (token && jwt.decode(token)) {
      const expiry = jwt.decode(token).exp;
      const now = new Date();
      return now.getTime() > expiry * 1000;
    }
    return false;

you can use npm install jsonwebtoken or some other npm package on the client side to do this

Create and endpoint that verifies the token is valid. You can use the the jsonwebtoken package.

import jwt from 'jsonwebtoken';

const verifyToken = (req, res) => {
  const token = req.headers.authorization;
  jwt.verify(token, SECRET_KEY, (err, decoded) => {
    if (err) {
      return res.status(401).send();
    }
    // can do something with the decoded data
  })
}

router.post('/verify-token', verifyToken);

I found a better option with promise to check if my token is valid

    jwt.verify(token,key,(err,result)=>{
    if(err){
        if(err.name == "TokenExpiredError"){
            console.log("Expired") //This case is when token expired
        }
        else{
            console.log(err.name) //Any other case
        }
    }
    else{
        //Here code for your promise using 'result' when token is Valid
    }
})

EDIT: this code is OK if you don't use the JWT for security reason, only if you use it to public stuff. since this request is show to user if it valid or not, and if not why. I'm using it only to understand if object is still available for other reason. (and it's OK to be public)