Chrome's Local StorageArea API in Synchronous way for use in Chrome extensions. Replace 'chrome.storage.local' by 'chrome.storage.sync' if you want to use Sync StorageArea

chrome-local-storage-api.js

/**
 * Retrieve object from Chrome's Local StorageArea
 * @param {string} key 
 */
const getObjectFromLocalStorage = async function(key) {
  return new Promise((resolve, reject) => {
    try {
      chrome.storage.local.get(key, function(value) {
        resolve(value[key]);
      });
    } catch (ex) {
      reject(ex);
    }
  });
};

/**
 * Save Object in Chrome's Local StorageArea
 * @param {*} obj 
 */
const saveObjectInLocalStorage = async function(obj) {
  return new Promise((resolve, reject) => {
    try {
      chrome.storage.local.set(obj, function() {
        resolve();
      });
    } catch (ex) {
      reject(ex);
    }
  });
};

/**
 * Removes Object from Chrome Local StorageArea.
 *
 * @param {string or array of string keys} keys
 */
const removeObjectFromLocalStorage = async function(keys) {
  return new Promise((resolve, reject) => {
    try {
      chrome.storage.local.remove(keys, function() {
        resolve();
      });
    } catch (ex) {
      reject(ex);
    }
  });
};

export {
  getObjectFromLocalStorage,
  saveObjectInLocalStorage,
  removeObjectFromLocalStorage
}

sample-use.js

import { getObjectFromLocalStorage, saveObjectInLocalStorage, removeObjectFromLocalStorage }  from './chrome-local-storage-api.js';

async function sampleUse() {
  let sampleObject = {
    'key-one': 1,
    'key-two': 'xyz'
  };
  
  await saveObjectInLocalStorage(sampleObject);
  
  console.log(await getObjectFromLocalStorage('key-one'));
  
  console.log(await getObjectFromLocalStorage('key-two'));
  await removeObjectFromLocalStorage('key-two');
  console.log(await getObjectFromLocalStorage('key-two'));
}

sampleUse();

It's not synchronous. It just eliminates callbacks.