Sessions in token based authentication

What I usually do is to keep the token in the local storage, this way I can persist the token even if the user leaves the site.

localStorage.setItem('app-token', theTokenFromServer);

Every time the user loads the page, the first thing I do is to look for the existence of the token.

token = localStorage.getItem('app-token');

If using react, I'd keep the token on the global state (using redux for example):

function loadAppToken(token) {
  return {
    type: 'LOAD_TOKEN',
    payload: { token },
  };
}

With vanilla javascript I'd keep it on my connection utility. Which might look something like the following:

const token = localStorage.getItem('app-token');

export function request(config) {
   const { url, ...others } = config;

   return fetch(url, {
     ...others,
     credentials: 'include',
     headers: {
       'Authorization': `Bearer ${token}`
     },
   });
}

I'd still have a fetch utility in a react app, similar to the previous code, but I'd send the token in the options, by getting it in a redux middleware for every single request.