Convert the `ViewHistory` to an ES6 class

web/view_history.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-var DEFAULT_VIEW_HISTORY_CACHE_SIZE = 20;
+const DEFAULT_VIEW_HISTORY_CACHE_SIZE = 20;
 
 /**
  * View History - This is a utility for saving various view parameters for
@@ -24,13 +24,12 @@ var DEFAULT_VIEW_HISTORY_CACHE_SIZE = 20;
  *  - FIREFOX or MOZCENTRAL - uses sessionStorage.
  *  - GENERIC or CHROME     - uses localStorage, if it is available.
  */
-var ViewHistory = (function ViewHistoryClosure() {
-  function ViewHistory(fingerprint, cacheSize) {
+class ViewHistory {
+  constructor(fingerprint, cacheSize = DEFAULT_VIEW_HISTORY_CACHE_SIZE) {
     this.fingerprint = fingerprint;
-    this.cacheSize = cacheSize || DEFAULT_VIEW_HISTORY_CACHE_SIZE;
+    this.cacheSize = cacheSize;
     this.isInitializedPromiseResolved = false;
-    this.initializedPromise =
-        this._readFromStorage().then(function (databaseStr) {
+    this.initializedPromise = this._readFromStorage().then((databaseStr) => {
       this.isInitializedPromiseResolved = true;
 
       var database = JSON.parse(databaseStr || '{}');
@@ -53,12 +52,11 @@ var ViewHistory = (function ViewHistoryClosure() {
       }
       this.file = database.files[index];
       this.database = database;
-    }.bind(this));
+    });
   }
 
-  ViewHistory.prototype = {
-    _writeToStorage: function ViewHistory_writeToStorage() {
-      return new Promise(function (resolve) {
+  _writeToStorage() {
+    return new Promise((resolve) => {
       var databaseStr = JSON.stringify(this.database);
 
       if (typeof PDFJSDev !== 'undefined' &&
@@ -68,10 +66,10 @@ var ViewHistory = (function ViewHistoryClosure() {
         localStorage.setItem('pdfjs.history', databaseStr);
       }
       resolve();
-      }.bind(this));
-    },
+    });
+  }
 
-    _readFromStorage: function ViewHistory_readFromStorage() {
+  _readFromStorage() {
     return new Promise(function(resolve) {
       if (typeof PDFJSDev !== 'undefined' &&
           PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
@@ -81,7 +79,7 @@ var ViewHistory = (function ViewHistoryClosure() {
 
         // TODO: Remove this key-name conversion after a suitable time-frame.
         // Note that we only remove the old 'database' entry if it looks like
-          // it was created by PDF.js. to avoid removing someone else's data.
+        // it was created by PDF.js, to avoid removing someone else's data.
         if (!value) {
           var databaseStr = localStorage.getItem('database');
           if (databaseStr) {
@@ -95,21 +93,20 @@ var ViewHistory = (function ViewHistoryClosure() {
             } catch (ex) { }
           }
         }
-
         resolve(value);
       }
     });
-    },
+  }
 
-    set: function ViewHistory_set(name, val) {
+  set(name, val) {
     if (!this.isInitializedPromiseResolved) {
       return;
     }
     this.file[name] = val;
     return this._writeToStorage();
-    },
+  }
 
-    setMultiple: function ViewHistory_setMultiple(properties) {
+  setMultiple(properties) {
     if (!this.isInitializedPromiseResolved) {
       return;
     }
@@ -117,18 +114,15 @@ var ViewHistory = (function ViewHistoryClosure() {
       this.file[name] = properties[name];
     }
     return this._writeToStorage();
-    },
+  }
 
-    get: function ViewHistory_get(name, defaultValue) {
+  get(name, defaultValue) {
     if (!this.isInitializedPromiseResolved) {
       return defaultValue;
     }
     return this.file[name] || defaultValue;
   }
-  };
-
-  return ViewHistory;
-})();
+}
 
 export {
   ViewHistory,