Very generic but working implementation of session storage fallback for safari in privacy mode

safari-privacy-mode-session-storage-polyfill.js

		submission = {
			handle: function (event) {
				event.preventDefault();
				event.stopPropagation();
				var id,
					data,
					storage = submission.getStorage(),
					nextUrl;

				data = storage.getItem('Opeepl');
				if (data === null) {
					data = {};
				} else {
					data = JSON.parse(data);
				}
				id = $('[name*=__identity]').val();
				data[id] = $(this).serializeArray();
				storage.setItem('Opeepl', JSON.stringify(data));
				nextUrl = OPEEPL.next(data[id]);
				if (nextUrl) {
					window.location.replace(nextUrl);
				} else {
					storage.clear();
 						OPEEPL.submit(data);
				}
				return false;
			},

			sessionStorageAvailable: function () {
				var storageTestKey = 'sTest',
					storage = sessionStorage;

				try {
					storage.setItem(storageTestKey, 'test');
					storage.removeItem(storageTestKey);
					return true;
				} catch (e) {
//					Just in case this isnt only ios specific we log it
//					if (e.code !== 22 && storage.length === 0) {
//						throw e;
//					}
					track(e);
					return false;
				}
			},

			getStorage: function () {
				var storage;

				if (submission.sessionStorageAvailable()) {
					storage = sessionStorage;
				} else {
					storage = {
						getItem: function (name) {
							var value;
							//just ignore name for now
							if (window.name.length === 0) {
								value = null;
							} else {
								value = window.name;
							}
							return value;
						},
						setItem: function (name, data) {
							window.name = data;
						},
						clear: function () {
							window.name = '';
						}
					};
				}
				return storage;
			}

part of larger script, but shows the concept.