diff --git a/calc.html b/calc.html
index 1c777ba2151cd412071414389740358746f4c01e..16a729c88526fbd9fe2a76cbc59c2e7dc75009fc 100644
--- a/calc.html
+++ b/calc.html
@@ -143,7 +143,10 @@
 	<div id="stack-content"></div>
       </div>
       <div id="keyboard">
-	<p>Keyboard <a title="reset RPN calculator" id="reset" href="#">Reset All</a></p>
+	<p>Keyboard
+	  <a title="reset RPN calculator" id="reset" href="#">Reset All</a>
+	  <a title="refresh page" id="refresh-page" href="#">Refresh Page</a>
+	</p>
 	<div class="keyboard">
 	  <table>
 	    <tr>
@@ -156,13 +159,13 @@
 	      <td data-bt-name="num7">7</td>
 	      <td data-bt-name="num8">8</td>
 	      <td data-bt-name="num9">9</td>
-	      <td title="delete pending digit or number in stack (q)" data-bt-name="backspace">←</td>
+	      <td title="delete pending digit or last number in stack (q)" data-bt-name="backspace">←</td>
 	    </tr>
 	    <tr>
 	      <td data-bt-name="num4">4</td>
 	      <td data-bt-name="num5">5</td>
 	      <td data-bt-name="num6">6</td>
-	      <td title="times" data-bt-name="times">*</td>
+	      <td title="times (*)" data-bt-name="times">×</td>
 	    </tr>
 	    <tr>
 	      <td data-bt-name="num1">1</td>
@@ -197,11 +200,24 @@
 	<div id="trail-content"></div>
       </div>
     </div>
+    <script type="text/javascript" src="vendor/localforage.min.js"></script>
     <script type="text/javascript" src="vendor/jquery.min.js"></script>
     <script type="text/javascript" src="fifo.js"></script>
     <script type="text/javascript" src="fsm.js"></script> <!-- fifo.js is required by fsm.js -->
     <script type="text/javascript">
       (function () {
+	  const testing = false;
+	  const uiTesting = false;
+
+	  // service worker
+	  if ('serviceWorker' in navigator) {
+	      navigator.serviceWorker
+		  .register('sw.js', {scope: './'})
+		  .then(function() {
+		      console.log("Service Worker Registered");
+		  });
+	  }
+
 	  /**
 	   * show dumb data for UI testing.
 	   */
@@ -555,11 +571,15 @@
 	  };
 
 	  // page init
-	  runTests();
+	  if (testing) {
+	      runTests();
+	  }
 
 	  const rpnCalculator = new fsm.RPNCalculator();
 
-	  // showDumbData(rpnCalculator);
+	  if (uiTesting) {
+	      showDumbData(rpnCalculator);
+	  }
 	  // init web UI
 	  updateUI(rpnCalculator);
 
@@ -590,6 +610,37 @@
 	      updateUI(rpnCalculator);
 	      return false;
 	  });
+	  $('#refresh-page').click(function (evt) {
+	      const urlJoin = function (baseUrl, path) {
+		  const lastSlash = baseUrl.lastIndexOf("/");
+		  return baseUrl.substring(0, lastSlash + 1) + path;
+	      };
+	      console.assert(urlJoin("http://localhost:8000/calc.html", "fifo.js") ===
+			     "http://localhost:8000/fifo.js");
+	      console.assert(urlJoin("http://localhost:8000/", "fifo.js") ===
+			     "http://localhost:8000/fifo.js");
+	      console.assert(urlJoin("http://localhost:8000/abc/t1.html", "fifo.js") ===
+			     "http://localhost:8000/abc/fifo.js");
+	      console.assert(urlJoin("https://www.example.com/calc.html", "fifo.js") ===
+			     "https://www.example.com/fifo.js");
+	      console.assert(urlJoin("https://www.example.com/", "fifo.js") ===
+			     "https://www.example.com/fifo.js");
+
+	      // set service worker cache to expire, thus fetching latest page on next refresh.
+	      const htmlUrl = window.location.href;
+	      const fifoJsUrl = urlJoin(htmlUrl, 'fifo.js');
+	      const fsmJsUrl = urlJoin(htmlUrl, 'fsm.js');
+	      // clear cache in page load order. the basic dependence should
+	      // be cleared first before trigger a page reload.
+	      localforage.setItem('timestamp:' + fsmJsUrl, new Date(2016,0,1).toJSON()).then(function (_) {
+		  localforage.setItem('timestamp:' + fifoJsUrl, new Date(2016,0,1).toJSON()).then(function (_) {
+		      localforage.setItem('timestamp:' + htmlUrl, new Date(2016,0,1).toJSON()).then(function (_) {
+			  window.location.href = window.location.href;
+		      });
+		  });
+	      });
+	      return false;
+	  });
 	  $('#expand-stack').click(function (evt) {
 	      const oldMaxHeight = $('#stack-content').css("max-height");
 	      if (oldMaxHeight === "100px") {
@@ -599,6 +650,7 @@
 		  $('#stack-content').css("max-height", "100px");
 		  $('#expand-stack').text("Expand Stack");
 	      }
+	      return false;
 	  });
 	  $('#expand-trail').click(function (evt) {
 	      const oldMaxHeight = $('#trail-content').css("max-height");
@@ -609,6 +661,7 @@
 		  $('#trail-content').css("max-height", "300px");
 		  $('#expand-trail').text("Shrink Trail");
 	      }
+	      return false;
 	  });
 	  $(document).keypress(function (evt) {
 	      // map evt.key to RPNCalculator keyName.
diff --git a/operational b/operational
index 8b657de57682cff69a4e9516881e4692625d1cff..497a01ea828bb1a37a598c376458313097587412 100644
--- a/operational
+++ b/operational
@@ -1,6 +1,6 @@
 * COMMENT -*- mode: org -*-
 #+Date: 2017-01-26
-Time-stamp: <2017-01-27>
+Time-stamp: <2017-01-28>
 #+STARTUP: content
 * notes                                                               :entry:
 ** 2017-01-27 steps to add new operator button.				:doc:
@@ -79,13 +79,6 @@ add "about" button beside "Reset All".
   version and source code location.
 - 
 
-** 2017-01-26 make it work offline, add sw.js
-- cache calc.html, fifo.js, fsm.js.
-  try update cache when cached page is more than 1d old.
-- cache vendor/* indefinitely.
-  do not check for update.
-  I think I can use version to handle this when I do upgrade vendor assets.
-
 ** 2017-01-27 deploy on https://rpn.emacsos.com/
 - I considered https://www.emacsos.com/rpn-calculator.html, but I don't want
   to mess up with sw.js scope issue.
@@ -101,6 +94,16 @@ should set a max-width on #number-display.
 overflow: auto
 doesn't work with <td> in firefox.
 * done                                                                :entry:
+** 2017-01-26 make it work offline, add sw.js
+- cache calc.html, fifo.js, fsm.js.
+  try update cache when cached page is more than 1d old.
+- cache vendor/* indefinitely.
+  do not check for update.
+  I think I can use version to handle this when I do upgrade vendor assets.
+- implementation notes
+  - see previous example in phonebookhs project.
+    ~/projects/phone-book/phonebook/static/js/sw.js
+
 ** 2017-01-27 bug: ** is not supported in firefox.
 use Math.pow() instead.
 
diff --git a/sw.js b/sw.js
new file mode 100644
index 0000000000000000000000000000000000000000..dd9118dddea2f38fca227cd6ac99a4081057f3d4
--- /dev/null
+++ b/sw.js
@@ -0,0 +1,177 @@
+importScripts('vendor/localforage.min.js');
+
+var CACHE = 'calc';
+
+/**
+ * get path from URL.
+ * drop schema, host, query string.
+ */
+const getUrlPath = function (url) {
+    var path = '/' + url.split('/').slice(3).join('/');
+    var paramIndex = path.indexOf('?');
+    if (paramIndex !== -1) {
+	return path.substring(0, paramIndex);
+    }
+    return path;
+};
+const cachePathList = ['/', '/calc.html'];
+const cacheFileExtList = ['.js', '.css', '.png', '.jpg', '.gif'];
+/**
+ * return true if this URL should be cached by service worker.
+ */
+const shouldCache = function (url) {
+    const path = getUrlPath(url);
+    if (cachePathList.indexOf(path) !== -1) {
+    	return true;
+    }
+    return cacheFileExtList.some(function (ext, index, ar) {
+    	return path.endsWith(ext);
+    });
+};
+/**
+ * return true if this URL is a vendor asset.
+ */
+const isVendorAsset = function (url) {
+    const path = getUrlPath(url);
+    return path.startsWith('/vendor/');
+};
+/**
+ * return true if this URL is static asset. see cacheFileExtList.
+ * files ending in those ext are considered to be static asset.
+ */
+const isStaticAsset = function (url) {
+    const path = getUrlPath(url);
+    if (path.endsWith('/sw.js')) {
+	return false;    // do not cache service worker js file.
+    }
+    return cacheFileExtList.some(function (ext, index, ar) {
+	return path.endsWith(ext);
+    });
+};
+
+/**
+ * cache timestamp key used in indexeddb.
+ * each cached url can have a cache timestamp with it.
+ */
+const cacheTimestampKey = function (url) {
+    return "timestamp:" + url;
+};
+
+// ===============
+//  event handler
+// ===============
+
+self.addEventListener('fetch', function(event) {
+    /**
+     * used as fetch(event.request)'s then function.
+     * cache the resp in service worker's req/resp cache, then return the resp.
+     *
+     * if response is not 2xx, do not cache.
+     */
+    const cacheRespAndReturn = function (resp) {
+	const respClone = resp.clone();
+	if (! resp.ok) {
+	    return resp;
+	}
+	caches.open(CACHE).then(function (cache) {
+	    cache.put(event.request, respClone);
+	    console.log("cached " + event.request.url);
+	});
+	return resp;
+    };
+
+    /**
+     * use cache if it exists. Otherwise, fetch and cache it.
+     */
+    const useServiceWorkerCache = function () {
+	return event.respondWith(
+	    caches.match(event.request).then(function (resp) {
+		if (resp) {
+		    return resp;
+		} else {
+		    return fetch(event.request).then(cacheRespAndReturn);
+		}
+	    })
+	);
+    };
+
+    /**
+     * use cached Response if it's not expired or when network is down.
+     * try renew cache if it's expired.
+     */
+    const useServiceWorkerCacheIfNotExpired = function () {
+	// console.log("use service worker cache if not expired");
+	const url = event.request.url;
+	const tsKey = cacheTimestampKey(url);
+	const expireSeconds = 24 * 3600;
+	/**
+	 * try update service worker req/resp cache and the ts cache.
+	 */
+	const tryUpdate = function () {
+	    return fetch(event.request).then(function (resp) {
+		const respClone = resp.clone();
+		if (! resp.ok) {
+		    console.log("HTTP ERROR: " + resp.status);
+		    return resp;    // just return, don't cache.
+		}
+		caches.open(CACHE).then(function (cache) {
+		    cache.put(event.request, respClone);
+		    console.log("cached " + event.request.url);
+		    const ts = new Date().toJSON();
+		    localforage.setItem(tsKey, ts).then(function () {
+			console.log("cache ts updated to " + ts + ", url=" + event.request.url);
+		    }).catch(function (err) {
+			console.log("cache ts update failed: " + err);
+		    });
+		});
+		return resp;
+	    }).catch(function (_err) {
+		console.log("fetch failed. try use cached resp.");
+		return caches.match(event.request);    // nothing to do if
+						       // match failed.
+	    });
+	};
+	return event.respondWith(
+	    localforage.getItem(tsKey).then(function (tsString) {
+		if (tsString !== null) {
+		    const now = new Date();
+		    const cacheDate = new Date(tsString);
+		    const diffSeconds = (now - cacheDate) / 1000;
+		    if (diffSeconds > expireSeconds) {
+			console.log("cache expired");
+			return tryUpdate();
+		    }
+		    console.log("cache is valid according to cache ts, url=",
+				event.request.url);
+		    return caches.match(event.request).then(function (resp) {
+			if (resp) {
+			    return resp;
+			}
+			return fetch(event.request);
+		    });
+		} else {
+		    console.log("no ts cache");
+		    return tryUpdate();
+		}
+	    }).catch(function (_err) {
+		console.log("no ts cache");
+		return tryUpdate();
+	    })
+	);
+    };
+
+    var url = event.request.url;
+
+    if (! shouldCache(url)) {
+	console.log("not caching " + url);
+	return fetch(event.request).catch(function (err) {
+	    console.log(err);
+	});
+    }
+    // console.log("will use sw cache on " + url);
+    if (isVendorAsset(url)) {
+	return useServiceWorkerCache();
+    } else {
+	return useServiceWorkerCacheIfNotExpired();
+    }
+});
diff --git a/vendor/localforage.min.js b/vendor/localforage.min.js
new file mode 100644
index 0000000000000000000000000000000000000000..9a233267fc7dfb648ead3f84e52d9ac704884df7
--- /dev/null
+++ b/vendor/localforage.min.js
@@ -0,0 +1,7 @@
+/*!
+    localForage -- Offline Storage, Improved
+    Version 1.4.3
+    https://mozilla.github.io/localForage
+    (c) 2013-2016 Mozilla, Apache License 2.0
+*/
+!function(a){if("object"==typeof exports&&"undefined"!=typeof module)module.exports=a();else if("function"==typeof define&&define.amd)define([],a);else{var b;b="undefined"!=typeof window?window:"undefined"!=typeof global?global:"undefined"!=typeof self?self:this,b.localforage=a()}}(function(){return function a(b,c,d){function e(g,h){if(!c[g]){if(!b[g]){var i="function"==typeof require&&require;if(!h&&i)return i(g,!0);if(f)return f(g,!0);var j=new Error("Cannot find module '"+g+"'");throw j.code="MODULE_NOT_FOUND",j}var k=c[g]={exports:{}};b[g][0].call(k.exports,function(a){var c=b[g][1][a];return e(c?c:a)},k,k.exports,a,b,c,d)}return c[g].exports}for(var f="function"==typeof require&&require,g=0;g<d.length;g++)e(d[g]);return e}({1:[function(a,b,c){"use strict";function d(){}function e(a){if("function"!=typeof a)throw new TypeError("resolver must be a function");this.state=s,this.queue=[],this.outcome=void 0,a!==d&&i(this,a)}function f(a,b,c){this.promise=a,"function"==typeof b&&(this.onFulfilled=b,this.callFulfilled=this.otherCallFulfilled),"function"==typeof c&&(this.onRejected=c,this.callRejected=this.otherCallRejected)}function g(a,b,c){o(function(){var d;try{d=b(c)}catch(b){return p.reject(a,b)}d===a?p.reject(a,new TypeError("Cannot resolve promise with itself")):p.resolve(a,d)})}function h(a){var b=a&&a.then;if(a&&"object"==typeof a&&"function"==typeof b)return function(){b.apply(a,arguments)}}function i(a,b){function c(b){f||(f=!0,p.reject(a,b))}function d(b){f||(f=!0,p.resolve(a,b))}function e(){b(d,c)}var f=!1,g=j(e);"error"===g.status&&c(g.value)}function j(a,b){var c={};try{c.value=a(b),c.status="success"}catch(a){c.status="error",c.value=a}return c}function k(a){return a instanceof this?a:p.resolve(new this(d),a)}function l(a){var b=new this(d);return p.reject(b,a)}function m(a){function b(a,b){function d(a){g[b]=a,++h!==e||f||(f=!0,p.resolve(j,g))}c.resolve(a).then(d,function(a){f||(f=!0,p.reject(j,a))})}var c=this;if("[object Array]"!==Object.prototype.toString.call(a))return this.reject(new TypeError("must be an array"));var e=a.length,f=!1;if(!e)return this.resolve([]);for(var g=new Array(e),h=0,i=-1,j=new this(d);++i<e;)b(a[i],i);return j}function n(a){function b(a){c.resolve(a).then(function(a){f||(f=!0,p.resolve(h,a))},function(a){f||(f=!0,p.reject(h,a))})}var c=this;if("[object Array]"!==Object.prototype.toString.call(a))return this.reject(new TypeError("must be an array"));var e=a.length,f=!1;if(!e)return this.resolve([]);for(var g=-1,h=new this(d);++g<e;)b(a[g]);return h}var o=a(2),p={},q=["REJECTED"],r=["FULFILLED"],s=["PENDING"];b.exports=c=e,e.prototype.catch=function(a){return this.then(null,a)},e.prototype.then=function(a,b){if("function"!=typeof a&&this.state===r||"function"!=typeof b&&this.state===q)return this;var c=new this.constructor(d);if(this.state!==s){var e=this.state===r?a:b;g(c,e,this.outcome)}else this.queue.push(new f(c,a,b));return c},f.prototype.callFulfilled=function(a){p.resolve(this.promise,a)},f.prototype.otherCallFulfilled=function(a){g(this.promise,this.onFulfilled,a)},f.prototype.callRejected=function(a){p.reject(this.promise,a)},f.prototype.otherCallRejected=function(a){g(this.promise,this.onRejected,a)},p.resolve=function(a,b){var c=j(h,b);if("error"===c.status)return p.reject(a,c.value);var d=c.value;if(d)i(a,d);else{a.state=r,a.outcome=b;for(var e=-1,f=a.queue.length;++e<f;)a.queue[e].callFulfilled(b)}return a},p.reject=function(a,b){a.state=q,a.outcome=b;for(var c=-1,d=a.queue.length;++c<d;)a.queue[c].callRejected(b);return a},c.resolve=k,c.reject=l,c.all=m,c.race=n},{2:2}],2:[function(a,b,c){(function(a){"use strict";function c(){k=!0;for(var a,b,c=l.length;c;){for(b=l,l=[],a=-1;++a<c;)b[a]();c=l.length}k=!1}function d(a){1!==l.push(a)||k||e()}var e,f=a.MutationObserver||a.WebKitMutationObserver;if(f){var g=0,h=new f(c),i=a.document.createTextNode("");h.observe(i,{characterData:!0}),e=function(){i.data=g=++g%2}}else if(a.setImmediate||"undefined"==typeof a.MessageChannel)e="document"in a&&"onreadystatechange"in a.document.createElement("script")?function(){var b=a.document.createElement("script");b.onreadystatechange=function(){c(),b.onreadystatechange=null,b.parentNode.removeChild(b),b=null},a.document.documentElement.appendChild(b)}:function(){setTimeout(c,0)};else{var j=new a.MessageChannel;j.port1.onmessage=c,e=function(){j.port2.postMessage(0)}}var k,l=[];b.exports=d}).call(this,"undefined"!=typeof global?global:"undefined"!=typeof self?self:"undefined"!=typeof window?window:{})},{}],3:[function(a,b,c){(function(b){"use strict";"function"!=typeof b.Promise&&(b.Promise=a(1))}).call(this,"undefined"!=typeof global?global:"undefined"!=typeof self?self:"undefined"!=typeof window?window:{})},{1:1}],4:[function(a,b,c){"use strict";function d(a,b){if(!(a instanceof b))throw new TypeError("Cannot call a class as a function")}function e(){try{if("undefined"!=typeof indexedDB)return indexedDB;if("undefined"!=typeof webkitIndexedDB)return webkitIndexedDB;if("undefined"!=typeof mozIndexedDB)return mozIndexedDB;if("undefined"!=typeof OIndexedDB)return OIndexedDB;if("undefined"!=typeof msIndexedDB)return msIndexedDB}catch(a){}}function f(){try{return!!fa&&(!("undefined"!=typeof openDatabase&&"undefined"!=typeof navigator&&navigator.userAgent&&/Safari/.test(navigator.userAgent)&&!/Chrome/.test(navigator.userAgent))&&(fa&&"function"==typeof fa.open&&"undefined"!=typeof IDBKeyRange))}catch(a){return!1}}function g(){return"function"==typeof openDatabase}function h(){try{return"undefined"!=typeof localStorage&&"setItem"in localStorage&&localStorage.setItem}catch(a){return!1}}function i(a,b){a=a||[],b=b||{};try{return new Blob(a,b)}catch(f){if("TypeError"!==f.name)throw f;for(var c="undefined"!=typeof BlobBuilder?BlobBuilder:"undefined"!=typeof MSBlobBuilder?MSBlobBuilder:"undefined"!=typeof MozBlobBuilder?MozBlobBuilder:WebKitBlobBuilder,d=new c,e=0;e<a.length;e+=1)d.append(a[e]);return d.getBlob(b.type)}}function j(a,b){b&&a.then(function(a){b(null,a)},function(a){b(a)})}function k(a,b,c){"function"==typeof b&&a.then(b),"function"==typeof c&&a.catch(c)}function l(a){for(var b=a.length,c=new ArrayBuffer(b),d=new Uint8Array(c),e=0;e<b;e++)d[e]=a.charCodeAt(e);return c}function m(a){return new ia(function(b){var c=i([""]);a.objectStore(ja).put(c,"key"),a.onabort=function(a){a.preventDefault(),a.stopPropagation(),b(!1)},a.oncomplete=function(){var a=navigator.userAgent.match(/Chrome\/(\d+)/),c=navigator.userAgent.match(/Edge\//);b(c||!a||parseInt(a[1],10)>=43)}}).catch(function(){return!1})}function n(a){return"boolean"==typeof ga?ia.resolve(ga):m(a).then(function(a){return ga=a})}function o(a){var b=ha[a.name],c={};c.promise=new ia(function(a){c.resolve=a}),b.deferredOperations.push(c),b.dbReady?b.dbReady=b.dbReady.then(function(){return c.promise}):b.dbReady=c.promise}function p(a){var b=ha[a.name],c=b.deferredOperations.pop();c&&c.resolve()}function q(a,b){return new ia(function(c,d){if(a.db){if(!b)return c(a.db);o(a),a.db.close()}var e=[a.name];b&&e.push(a.version);var f=fa.open.apply(fa,e);b&&(f.onupgradeneeded=function(b){var c=f.result;try{c.createObjectStore(a.storeName),b.oldVersion<=1&&c.createObjectStore(ja)}catch(c){if("ConstraintError"!==c.name)throw c;console.warn('The database "'+a.name+'" has been upgraded from version '+b.oldVersion+" to version "+b.newVersion+', but the storage "'+a.storeName+'" already exists.')}}),f.onerror=function(){d(f.error)},f.onsuccess=function(){c(f.result),p(a)}})}function r(a){return q(a,!1)}function s(a){return q(a,!0)}function t(a,b){if(!a.db)return!0;var c=!a.db.objectStoreNames.contains(a.storeName),d=a.version<a.db.version,e=a.version>a.db.version;if(d&&(a.version!==b&&console.warn('The database "'+a.name+"\" can't be downgraded from version "+a.db.version+" to version "+a.version+"."),a.version=a.db.version),e||c){if(c){var f=a.db.version+1;f>a.version&&(a.version=f)}return!0}return!1}function u(a){return new ia(function(b,c){var d=new FileReader;d.onerror=c,d.onloadend=function(c){var d=btoa(c.target.result||"");b({__local_forage_encoded_blob:!0,data:d,type:a.type})},d.readAsBinaryString(a)})}function v(a){var b=l(atob(a.data));return i([b],{type:a.type})}function w(a){return a&&a.__local_forage_encoded_blob}function x(a){var b=this,c=b._initReady().then(function(){var a=ha[b._dbInfo.name];if(a&&a.dbReady)return a.dbReady});return k(c,a,a),c}function y(a){function b(){return ia.resolve()}var c=this,d={db:null};if(a)for(var e in a)d[e]=a[e];ha||(ha={});var f=ha[d.name];f||(f={forages:[],db:null,dbReady:null,deferredOperations:[]},ha[d.name]=f),f.forages.push(c),c._initReady||(c._initReady=c.ready,c.ready=x);for(var g=[],h=0;h<f.forages.length;h++){var i=f.forages[h];i!==c&&g.push(i._initReady().catch(b))}var j=f.forages.slice(0);return ia.all(g).then(function(){return d.db=f.db,r(d)}).then(function(a){return d.db=a,t(d,c._defaultConfig.version)?s(d):a}).then(function(a){d.db=f.db=a,c._dbInfo=d;for(var b=0;b<j.length;b++){var e=j[b];e!==c&&(e._dbInfo.db=d.db,e._dbInfo.version=d.version)}})}function z(a,b){var c=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo,f=e.db.transaction(e.storeName,"readonly").objectStore(e.storeName),g=f.get(a);g.onsuccess=function(){var a=g.result;void 0===a&&(a=null),w(a)&&(a=v(a)),b(a)},g.onerror=function(){d(g.error)}}).catch(d)});return j(d,b),d}function A(a,b){var c=this,d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo,f=e.db.transaction(e.storeName,"readonly").objectStore(e.storeName),g=f.openCursor(),h=1;g.onsuccess=function(){var c=g.result;if(c){var d=c.value;w(d)&&(d=v(d));var e=a(d,c.key,h++);void 0!==e?b(e):c.continue()}else b()},g.onerror=function(){d(g.error)}}).catch(d)});return j(d,b),d}function B(a,b,c){var d=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var e=new ia(function(c,e){var f;d.ready().then(function(){return f=d._dbInfo,"[object Blob]"===ka.call(b)?n(f.db).then(function(a){return a?b:u(b)}):b}).then(function(b){var d=f.db.transaction(f.storeName,"readwrite"),g=d.objectStore(f.storeName);null===b&&(b=void 0),d.oncomplete=function(){void 0===b&&(b=null),c(b)},d.onabort=d.onerror=function(){var a=h.error?h.error:h.transaction.error;e(a)};var h=g.put(b,a)}).catch(e)});return j(e,c),e}function C(a,b){var c=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo,f=e.db.transaction(e.storeName,"readwrite"),g=f.objectStore(e.storeName),h=g.delete(a);f.oncomplete=function(){b()},f.onerror=function(){d(h.error)},f.onabort=function(){var a=h.error?h.error:h.transaction.error;d(a)}}).catch(d)});return j(d,b),d}function D(a){var b=this,c=new ia(function(a,c){b.ready().then(function(){var d=b._dbInfo,e=d.db.transaction(d.storeName,"readwrite"),f=e.objectStore(d.storeName),g=f.clear();e.oncomplete=function(){a()},e.onabort=e.onerror=function(){var a=g.error?g.error:g.transaction.error;c(a)}}).catch(c)});return j(c,a),c}function E(a){var b=this,c=new ia(function(a,c){b.ready().then(function(){var d=b._dbInfo,e=d.db.transaction(d.storeName,"readonly").objectStore(d.storeName),f=e.count();f.onsuccess=function(){a(f.result)},f.onerror=function(){c(f.error)}}).catch(c)});return j(c,a),c}function F(a,b){var c=this,d=new ia(function(b,d){return a<0?void b(null):void c.ready().then(function(){var e=c._dbInfo,f=e.db.transaction(e.storeName,"readonly").objectStore(e.storeName),g=!1,h=f.openCursor();h.onsuccess=function(){var c=h.result;return c?void(0===a?b(c.key):g?b(c.key):(g=!0,c.advance(a))):void b(null)},h.onerror=function(){d(h.error)}}).catch(d)});return j(d,b),d}function G(a){var b=this,c=new ia(function(a,c){b.ready().then(function(){var d=b._dbInfo,e=d.db.transaction(d.storeName,"readonly").objectStore(d.storeName),f=e.openCursor(),g=[];f.onsuccess=function(){var b=f.result;return b?(g.push(b.key),void b.continue()):void a(g)},f.onerror=function(){c(f.error)}}).catch(c)});return j(c,a),c}function H(a){var b,c,d,e,f,g=.75*a.length,h=a.length,i=0;"="===a[a.length-1]&&(g--,"="===a[a.length-2]&&g--);var j=new ArrayBuffer(g),k=new Uint8Array(j);for(b=0;b<h;b+=4)c=ma.indexOf(a[b]),d=ma.indexOf(a[b+1]),e=ma.indexOf(a[b+2]),f=ma.indexOf(a[b+3]),k[i++]=c<<2|d>>4,k[i++]=(15&d)<<4|e>>2,k[i++]=(3&e)<<6|63&f;return j}function I(a){var b,c=new Uint8Array(a),d="";for(b=0;b<c.length;b+=3)d+=ma[c[b]>>2],d+=ma[(3&c[b])<<4|c[b+1]>>4],d+=ma[(15&c[b+1])<<2|c[b+2]>>6],d+=ma[63&c[b+2]];return c.length%3===2?d=d.substring(0,d.length-1)+"=":c.length%3===1&&(d=d.substring(0,d.length-2)+"=="),d}function J(a,b){var c="";if(a&&(c=Da.call(a)),a&&("[object ArrayBuffer]"===c||a.buffer&&"[object ArrayBuffer]"===Da.call(a.buffer))){var d,e=pa;a instanceof ArrayBuffer?(d=a,e+=ra):(d=a.buffer,"[object Int8Array]"===c?e+=ta:"[object Uint8Array]"===c?e+=ua:"[object Uint8ClampedArray]"===c?e+=va:"[object Int16Array]"===c?e+=wa:"[object Uint16Array]"===c?e+=ya:"[object Int32Array]"===c?e+=xa:"[object Uint32Array]"===c?e+=za:"[object Float32Array]"===c?e+=Aa:"[object Float64Array]"===c?e+=Ba:b(new Error("Failed to get type for BinaryArray"))),b(e+I(d))}else if("[object Blob]"===c){var f=new FileReader;f.onload=function(){var c=na+a.type+"~"+I(this.result);b(pa+sa+c)},f.readAsArrayBuffer(a)}else try{b(JSON.stringify(a))}catch(c){console.error("Couldn't convert value into a JSON string: ",a),b(null,c)}}function K(a){if(a.substring(0,qa)!==pa)return JSON.parse(a);var b,c=a.substring(Ca),d=a.substring(qa,Ca);if(d===sa&&oa.test(c)){var e=c.match(oa);b=e[1],c=c.substring(e[0].length)}var f=H(c);switch(d){case ra:return f;case sa:return i([f],{type:b});case ta:return new Int8Array(f);case ua:return new Uint8Array(f);case va:return new Uint8ClampedArray(f);case wa:return new Int16Array(f);case ya:return new Uint16Array(f);case xa:return new Int32Array(f);case za:return new Uint32Array(f);case Aa:return new Float32Array(f);case Ba:return new Float64Array(f);default:throw new Error("Unkown type: "+d)}}function L(a){var b=this,c={db:null};if(a)for(var d in a)c[d]="string"!=typeof a[d]?a[d].toString():a[d];var e=new ia(function(a,d){try{c.db=openDatabase(c.name,String(c.version),c.description,c.size)}catch(a){return d(a)}c.db.transaction(function(e){e.executeSql("CREATE TABLE IF NOT EXISTS "+c.storeName+" (id INTEGER PRIMARY KEY, key unique, value)",[],function(){b._dbInfo=c,a()},function(a,b){d(b)})})});return c.serializer=Ea,e}function M(a,b){var c=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo;e.db.transaction(function(c){c.executeSql("SELECT * FROM "+e.storeName+" WHERE key = ? LIMIT 1",[a],function(a,c){var d=c.rows.length?c.rows.item(0).value:null;d&&(d=e.serializer.deserialize(d)),b(d)},function(a,b){d(b)})})}).catch(d)});return j(d,b),d}function N(a,b){var c=this,d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo;e.db.transaction(function(c){c.executeSql("SELECT * FROM "+e.storeName,[],function(c,d){for(var f=d.rows,g=f.length,h=0;h<g;h++){var i=f.item(h),j=i.value;if(j&&(j=e.serializer.deserialize(j)),j=a(j,i.key,h+1),void 0!==j)return void b(j)}b()},function(a,b){d(b)})})}).catch(d)});return j(d,b),d}function O(a,b,c){var d=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var e=new ia(function(c,e){d.ready().then(function(){void 0===b&&(b=null);var f=b,g=d._dbInfo;g.serializer.serialize(b,function(b,d){d?e(d):g.db.transaction(function(d){d.executeSql("INSERT OR REPLACE INTO "+g.storeName+" (key, value) VALUES (?, ?)",[a,b],function(){c(f)},function(a,b){e(b)})},function(a){a.code===a.QUOTA_ERR&&e(a)})})}).catch(e)});return j(e,c),e}function P(a,b){var c=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo;e.db.transaction(function(c){c.executeSql("DELETE FROM "+e.storeName+" WHERE key = ?",[a],function(){b()},function(a,b){d(b)})})}).catch(d)});return j(d,b),d}function Q(a){var b=this,c=new ia(function(a,c){b.ready().then(function(){var d=b._dbInfo;d.db.transaction(function(b){b.executeSql("DELETE FROM "+d.storeName,[],function(){a()},function(a,b){c(b)})})}).catch(c)});return j(c,a),c}function R(a){var b=this,c=new ia(function(a,c){b.ready().then(function(){var d=b._dbInfo;d.db.transaction(function(b){b.executeSql("SELECT COUNT(key) as c FROM "+d.storeName,[],function(b,c){var d=c.rows.item(0).c;a(d)},function(a,b){c(b)})})}).catch(c)});return j(c,a),c}function S(a,b){var c=this,d=new ia(function(b,d){c.ready().then(function(){var e=c._dbInfo;e.db.transaction(function(c){c.executeSql("SELECT key FROM "+e.storeName+" WHERE id = ? LIMIT 1",[a+1],function(a,c){var d=c.rows.length?c.rows.item(0).key:null;b(d)},function(a,b){d(b)})})}).catch(d)});return j(d,b),d}function T(a){var b=this,c=new ia(function(a,c){b.ready().then(function(){var d=b._dbInfo;d.db.transaction(function(b){b.executeSql("SELECT key FROM "+d.storeName,[],function(b,c){for(var d=[],e=0;e<c.rows.length;e++)d.push(c.rows.item(e).key);a(d)},function(a,b){c(b)})})}).catch(c)});return j(c,a),c}function U(a){var b=this,c={};if(a)for(var d in a)c[d]=a[d];return c.keyPrefix=c.name+"/",c.storeName!==b._defaultConfig.storeName&&(c.keyPrefix+=c.storeName+"/"),b._dbInfo=c,c.serializer=Ea,ia.resolve()}function V(a){var b=this,c=b.ready().then(function(){for(var a=b._dbInfo.keyPrefix,c=localStorage.length-1;c>=0;c--){var d=localStorage.key(c);0===d.indexOf(a)&&localStorage.removeItem(d)}});return j(c,a),c}function W(a,b){var c=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var d=c.ready().then(function(){var b=c._dbInfo,d=localStorage.getItem(b.keyPrefix+a);return d&&(d=b.serializer.deserialize(d)),d});return j(d,b),d}function X(a,b){var c=this,d=c.ready().then(function(){for(var b=c._dbInfo,d=b.keyPrefix,e=d.length,f=localStorage.length,g=1,h=0;h<f;h++){var i=localStorage.key(h);if(0===i.indexOf(d)){var j=localStorage.getItem(i);if(j&&(j=b.serializer.deserialize(j)),j=a(j,i.substring(e),g++),void 0!==j)return j}}});return j(d,b),d}function Y(a,b){var c=this,d=c.ready().then(function(){var b,d=c._dbInfo;try{b=localStorage.key(a)}catch(a){b=null}return b&&(b=b.substring(d.keyPrefix.length)),b});return j(d,b),d}function Z(a){var b=this,c=b.ready().then(function(){for(var a=b._dbInfo,c=localStorage.length,d=[],e=0;e<c;e++)0===localStorage.key(e).indexOf(a.keyPrefix)&&d.push(localStorage.key(e).substring(a.keyPrefix.length));return d});return j(c,a),c}function $(a){var b=this,c=b.keys().then(function(a){return a.length});return j(c,a),c}function _(a,b){var c=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var d=c.ready().then(function(){var b=c._dbInfo;localStorage.removeItem(b.keyPrefix+a)});return j(d,b),d}function aa(a,b,c){var d=this;"string"!=typeof a&&(console.warn(a+" used as a key, but it is not a string."),a=String(a));var e=d.ready().then(function(){void 0===b&&(b=null);var c=b;return new ia(function(e,f){var g=d._dbInfo;g.serializer.serialize(b,function(b,d){if(d)f(d);else try{localStorage.setItem(g.keyPrefix+a,b),e(c)}catch(a){"QuotaExceededError"!==a.name&&"NS_ERROR_DOM_QUOTA_REACHED"!==a.name||f(a),f(a)}})})});return j(e,c),e}function ba(a,b){a[b]=function(){var c=arguments;return a.ready().then(function(){return a[b].apply(a,c)})}}function ca(){for(var a=1;a<arguments.length;a++){var b=arguments[a];if(b)for(var c in b)b.hasOwnProperty(c)&&(Na(b[c])?arguments[0][c]=b[c].slice():arguments[0][c]=b[c])}return arguments[0]}function da(a){for(var b in Ia)if(Ia.hasOwnProperty(b)&&Ia[b]===a)return!0;return!1}var ea="function"==typeof Symbol&&"symbol"==typeof Symbol.iterator?function(a){return typeof a}:function(a){return a&&"function"==typeof Symbol&&a.constructor===Symbol&&a!==Symbol.prototype?"symbol":typeof a},fa=e();"undefined"==typeof Promise&&"undefined"!=typeof a&&a(3);var ga,ha,ia=Promise,ja="local-forage-detect-blob-support",ka=Object.prototype.toString,la={_driver:"asyncStorage",_initStorage:y,iterate:A,getItem:z,setItem:B,removeItem:C,clear:D,length:E,key:F,keys:G},ma="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",na="~~local_forage_type~",oa=/^~~local_forage_type~([^~]+)~/,pa="__lfsc__:",qa=pa.length,ra="arbf",sa="blob",ta="si08",ua="ui08",va="uic8",wa="si16",xa="si32",ya="ur16",za="ui32",Aa="fl32",Ba="fl64",Ca=qa+ra.length,Da=Object.prototype.toString,Ea={serialize:J,deserialize:K,stringToBuffer:H,bufferToString:I},Fa={_driver:"webSQLStorage",_initStorage:L,iterate:N,getItem:M,setItem:O,removeItem:P,clear:Q,length:R,key:S,keys:T},Ga={_driver:"localStorageWrapper",_initStorage:U,iterate:X,getItem:W,setItem:aa,removeItem:_,clear:V,length:$,key:Y,keys:Z},Ha={},Ia={INDEXEDDB:"asyncStorage",LOCALSTORAGE:"localStorageWrapper",WEBSQL:"webSQLStorage"},Ja=[Ia.INDEXEDDB,Ia.WEBSQL,Ia.LOCALSTORAGE],Ka=["clear","getItem","iterate","key","keys","length","removeItem","setItem"],La={description:"",driver:Ja.slice(),name:"localforage",size:4980736,storeName:"keyvaluepairs",version:1},Ma={};Ma[Ia.INDEXEDDB]=f(),Ma[Ia.WEBSQL]=g(),Ma[Ia.LOCALSTORAGE]=h();var Na=Array.isArray||function(a){return"[object Array]"===Object.prototype.toString.call(a)},Oa=function(){function a(b){d(this,a),this.INDEXEDDB=Ia.INDEXEDDB,this.LOCALSTORAGE=Ia.LOCALSTORAGE,this.WEBSQL=Ia.WEBSQL,this._defaultConfig=ca({},La),this._config=ca({},this._defaultConfig,b),this._driverSet=null,this._initDriver=null,this._ready=!1,this._dbInfo=null,this._wrapLibraryMethodsWithReady(),this.setDriver(this._config.driver)}return a.prototype.config=function(a){if("object"===("undefined"==typeof a?"undefined":ea(a))){if(this._ready)return new Error("Can't call config() after localforage has been used.");for(var b in a)"storeName"===b&&(a[b]=a[b].replace(/\W/g,"_")),this._config[b]=a[b];return"driver"in a&&a.driver&&this.setDriver(this._config.driver),!0}return"string"==typeof a?this._config[a]:this._config},a.prototype.defineDriver=function(a,b,c){var d=new ia(function(b,c){try{var d=a._driver,e=new Error("Custom driver not compliant; see https://mozilla.github.io/localForage/#definedriver"),f=new Error("Custom driver name already in use: "+a._driver);if(!a._driver)return void c(e);if(da(a._driver))return void c(f);for(var g=Ka.concat("_initStorage"),h=0;h<g.length;h++){var i=g[h];if(!i||!a[i]||"function"!=typeof a[i])return void c(e)}var j=ia.resolve(!0);"_support"in a&&(j=a._support&&"function"==typeof a._support?a._support():ia.resolve(!!a._support)),j.then(function(c){Ma[d]=c,Ha[d]=a,b()},c)}catch(a){c(a)}});return k(d,b,c),d},a.prototype.driver=function(){return this._driver||null},a.prototype.getDriver=function(a,b,c){var d=this,e=ia.resolve().then(function(){if(!da(a)){if(Ha[a])return Ha[a];throw new Error("Driver not found.")}switch(a){case d.INDEXEDDB:return la;case d.LOCALSTORAGE:return Ga;case d.WEBSQL:return Fa}});return k(e,b,c),e},a.prototype.getSerializer=function(a){var b=ia.resolve(Ea);return k(b,a),b},a.prototype.ready=function(a){var b=this,c=b._driverSet.then(function(){return null===b._ready&&(b._ready=b._initDriver()),b._ready});return k(c,a,a),c},a.prototype.setDriver=function(a,b,c){function d(){f._config.driver=f.driver()}function e(a){return function(){function b(){for(;c<a.length;){var e=a[c];return c++,f._dbInfo=null,f._ready=null,f.getDriver(e).then(function(a){return f._extend(a),d(),f._ready=f._initStorage(f._config),f._ready}).catch(b)}d();var g=new Error("No available storage method found.");return f._driverSet=ia.reject(g),f._driverSet}var c=0;return b()}}var f=this;Na(a)||(a=[a]);var g=this._getSupportedDrivers(a),h=null!==this._driverSet?this._driverSet.catch(function(){return ia.resolve()}):ia.resolve();return this._driverSet=h.then(function(){var a=g[0];return f._dbInfo=null,f._ready=null,f.getDriver(a).then(function(a){f._driver=a._driver,d(),f._wrapLibraryMethodsWithReady(),f._initDriver=e(g)})}).catch(function(){d();var a=new Error("No available storage method found.");return f._driverSet=ia.reject(a),f._driverSet}),k(this._driverSet,b,c),this._driverSet},a.prototype.supports=function(a){return!!Ma[a]},a.prototype._extend=function(a){ca(this,a)},a.prototype._getSupportedDrivers=function(a){for(var b=[],c=0,d=a.length;c<d;c++){var e=a[c];this.supports(e)&&b.push(e)}return b},a.prototype._wrapLibraryMethodsWithReady=function(){for(var a=0;a<Ka.length;a++)ba(this,Ka[a])},a.prototype.createInstance=function(b){return new a(b)},a}(),Pa=new Oa;b.exports=Pa},{3:3}]},{},[4])(4)});
\ No newline at end of file