modernizr/feature-detects/storage/localstorage.js

Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.

/*!
{
  "name": "Local Storage",
  "property": "localstorage",
  "caniuse": "namevalue-storage",
  "tags": ["storage"],
  "knownBugs": [],
  "notes": [],
  "warnings": [],
  "polyfills": [
    "joshuabell-polyfill",
    "cupcake",
    "storagepolyfill",
    "amplifyjs",
    "yui-cacheoffline"
  ]
}
!*/
define(['Modernizr'], function(Modernizr) {
  // In FF4, if disabled, window.localStorage should === null.

  // Normally, we could not test that directly and need to do a
  //   `('localStorage' in window)` test first because otherwise Firefox will
  //   throw bugzil.la/365772 if cookies are disabled

  // Similarly, in Chrome with "Block third-party cookies and site data" enabled,
  // attempting to access `window.sessionStorage` will throw an exception. crbug.com/357625

  // Also in iOS5 Private Browsing mode, attempting to use localStorage.setItem
  // will throw the exception:
  //   QUOTA_EXCEEDED_ERROR DOM Exception 22.
  // Peculiarly, getItem and removeItem calls do not throw.

  // Because we are forced to try/catch this, we'll go aggressive.

  // Just FWIW: IE8 Compat mode supports these features completely:
  //   www.quirksmode.org/dom/html5.html
  // But IE8 doesn't support either with local files

  Modernizr.addTest('localstorage', function() {
    var mod = 'modernizr';
    try {
      localStorage.setItem(mod, mod);
      localStorage.removeItem(mod);
      return true;
    } catch (e) {
      return false;
    }
  });
});