Get an Object of sessionStorage data set by Salesforce Components. Should be able to work for localStorage too

salesforce-session-storage.js

function getSfSessionStorage() {
  let sfSessionStorage = {};

  // find the sessionStorage key that hold the SF data
  Object.keys(sessionStorage).forEach((key) => {
    if (key.includes('namespace')) {
      sfSessionStorage = JSON.parse(sessionStorage[key]);
    }
  });

  let sfSessionStorageData = {};
  // loop over each sf object key
  Object.keys(sfSessionStorage).forEach((sfKey) => {
    // get the index of the sessionStorage from the sfSessionStorage object
    const sessionStorageIndex = sfSessionStorage[sfKey];

    // check the index exists
    if (sessionStorage.hasOwnProperty(sessionStorageIndex)) {
      // find the data with the sfKey
      const item = sessionStorage[sessionStorageIndex]

      // merge in the data + attempt to parse it
      sfSessionStorageData = {
        ...sfSessionStorageData,
        ...{
          [sfKey]: item && JSON.parse(item),
        },
      };
    }
  });

  return sfSessionStorageData;
}