Calculates localStorage key and total size occupied by data in MB

local_storage_size.js

function sizeInMB(string) {
  return (string.length * 2) / (1024 * 1024);
}

function addKeySizeToTotal(runningTotal, key) { 
  // Used as Array.reduce callback
  return sizeInMB(localStorage[key]) + runningTotal;
}

function logLocalStorageKeySize(key) {
 console.log(key + ' = ' + sizeInMB(localStorage[key]).toFixed(2) + ' MB');
}

function logLocalStorageSizeInfo() {
  var localStorageKeys = Object.keys(localStorage);
  localStorageKeys.map(logLocalStorageKeySize);
  var localStorageSizeInMB = localStorageKeys.reduce(addKeySizeToTotal, 0);
  console.log('total = ' + localStorageSizeInMB.toFixed(2) + ' MB');
}

logLocalStorageSizeInfo();