How to store jwt token in localStorage and send it back to the server with header in express?

You can store your jwt token in localstorage and when ever you make a API call you can add the token to headers as token. if you are using axios you can attach you token to headers like this. Here the token is stored in localstorage with the key 'jwtToken'

  axios.post('http://yourendpoint',data,{ headers: { Authorization:localStorage.getItem('jwtToken') } })
            .then(response=> console.log(response))
            .catch(error => console.log(error));
   };

First you have to create or Generate Token through Jwt (jsonWebTokens) then either store it in local Storage or through Cookie or through Session. I generally prefer local storage because it is easier to store token in local storage through SET and retrieve it using GET method. and after retrieving it through get you can verify it through jwt and also authenticate it with bearer authentication..

And for headers add Authorization

fetch("/users", {
  method: "Get",
  headers: {
    "content-type": "application/json",
    Authorization: "Bearer" + localStorage.getItem("token")
  }