ctwowt · April 18, 2020 04:54 · Jan 8, 2020 · Jan 8, 2020 · Sep 27, 2019 · Sep 25, 2019
diff --git a/idb-backup-and-restore.md b/idb-backup-and-restore.md
@@ -41,6 +41,7 @@ Depending on your use case, it can be reasonable to clear a database before impo
 
 ```js
 import { idb } from 'some-database'
+import { serializedData } from 'some-serialized-data'
 
 import { importFromJson, clearDatabase } from 'idb-backup-and-restore.mjs'
 

diff --git a/idb-backup-and-restore.md b/idb-backup-and-restore.md
@@ -7,9 +7,9 @@ For each of the provided functionalities, you need a connected [`IDBDatabase`](h
 
 ### Export Data
 ```js
-import { idb } from 'get-database-from-somewhere.js'
+import { idb } from 'some-database'
 
-import { exportToJson } from 'idb-backup-and-restore.js'
+import { exportToJson } from 'idb-backup-and-restore.mjs'
 
 exportToJson(idb)
   .then(result => {
@@ -22,10 +22,10 @@ exportToJson(idb)
 
 ### Import Data
 ```js
-import { idb } from 'get-database-from-somewhere.js'
-import { serializedData } from 'get-serialized-data-from-somewhere.js'
+import { idb } from 'some-database'
+import { serializedData } from 'some-serialized-data'
 
-import { importFromJson } from 'idb-backup-and-restore.js'
+import { importFromJson } from 'idb-backup-and-restore.mjs'
 
 importFromJson(idb, serializedData)
   .then(() => {
@@ -40,10 +40,9 @@ importFromJson(idb, serializedData)
 Depending on your use case, it can be reasonable to clear a database before importing serialized data:
 
 ```js
-import { idb } from 'get-database-from-somewhere.js'
-import { serializedData } from 'get-serialized-data-from-somewhere.js'
+import { idb } from 'some-database'
 
-import { importFromJson, clearDatabase } from 'idb-backup-and-restore.js'
+import { importFromJson, clearDatabase } from 'idb-backup-and-restore.mjs'
 
 clearDatabase(idb)
   .then(() => importFromJson(idb, serializedData))

diff --git a/readme.md → idb-backup-and-restore.md b/readme.md → idb-backup-and-restore.md
diff --git a/idb-backup-and-restore.js → idb-backup-and-restore.mjs b/idb-backup-and-restore.js → idb-backup-and-restore.mjs
diff --git a/idb-backup-and-restore.js b/idb-backup-and-restore.js
@@ -90,23 +90,25 @@ export function importFromJson(idbDatabase, json) {
  * @return {Promise<void>}
  */
 export function clearDatabase(idbDatabase) {
-  const transaction = idbDatabase.transaction(
-    idbDatabase.objectStoreNames,
-    'readwrite'
-  )
-  transaction.addEventListener('error', reject)
+  return new Promise((resolve, reject) => {
+    const transaction = idbDatabase.transaction(
+      idbDatabase.objectStoreNames,
+      'readwrite'
+    )
+    transaction.addEventListener('error', reject)
 
-  let count = 0
-  for (const storeName of idbDatabase.objectStoreNames) {
-    transaction
-      .objectStore(storeName)
-      .clear()
-      .addEventListener('success', () => {
-        count++
-        if (count === idbDatabase.objectStoreNames.length) {
-          // Cleared all object stores
-          resolve()
-        }
-      })
-  }
+    let count = 0
+    for (const storeName of idbDatabase.objectStoreNames) {
+      transaction
+        .objectStore(storeName)
+        .clear()
+        .addEventListener('success', () => {
+          count++
+          if (count === idbDatabase.objectStoreNames.length) {
+            // Cleared all object stores
+            resolve()
+          }
+        })
+    }
+  })
 }
diff --git a/idb-backup-and-restore.js b/idb-backup-and-restore.js
@@ -0,0 +1,112 @@
+/**
+ * Export all data from an IndexedDB database
+ *
+ * @param {IDBDatabase} idbDatabase The database to export from
+ * @return {Promise<string>}
+ */
+export function exportToJson(idbDatabase) {
+  return new Promise((resolve, reject) => {
+    const exportObject = {}
+    if (idbDatabase.objectStoreNames.length === 0) {
+      resolve(JSON.stringify(exportObject))
+    } else {
+      const transaction = idbDatabase.transaction(
+        idbDatabase.objectStoreNames,
+        'readonly'
+      )
+
+      transaction.addEventListener('error', reject)
+
+      for (const storeName of idbDatabase.objectStoreNames) {
+        const allObjects = []
+        transaction
+          .objectStore(storeName)
+          .openCursor()
+          .addEventListener('success', event => {
+            const cursor = event.target.result
+            if (cursor) {
+              // Cursor holds value, put it into store data
+              allObjects.push(cursor.value)
+              cursor.continue()
+            } else {
+              // No more values, store is done
+              exportObject[storeName] = allObjects
+
+              // Last store was handled
+              if (
+                idbDatabase.objectStoreNames.length ===
+                Object.keys(exportObject).length
+              ) {
+                resolve(JSON.stringify(exportObject))
+              }
+            }
+          })
+      }
+    }
+  })
+}
+
+/**
+ * Import data from JSON into an IndexedDB database.
+ * This does not delete any existing data from the database, so keys may clash.
+ *
+ * @param {IDBDatabase} idbDatabase Database to import into
+ * @param {string}      json        Data to import, one key per object store
+ * @return {Promise<void>}
+ */
+export function importFromJson(idbDatabase, json) {
+  return new Promise((resolve, reject) => {
+    const transaction = idbDatabase.transaction(
+      idbDatabase.objectStoreNames,
+      'readwrite'
+    )
+    transaction.addEventListener('error', reject)
+
+    var importObject = JSON.parse(json)
+    for (const storeName of idbDatabase.objectStoreNames) {
+      let count = 0
+      for (const toAdd of importObject[storeName]) {
+        const request = transaction.objectStore(storeName).add(toAdd)
+        request.addEventListener('success', () => {
+          count++
+          if (count === importObject[storeName].length) {
+            // Added all objects for this store
+            delete importObject[storeName]
+            if (Object.keys(importObject).length === 0) {
+              // Added all object stores
+              resolve()
+            }
+          }
+        })
+      }
+    }
+  })
+}
+
+/**
+ * Clear a database
+ *
+ * @param {IDBDatabase} idbDatabase The database to delete all data from
+ * @return {Promise<void>}
+ */
+export function clearDatabase(idbDatabase) {
+  const transaction = idbDatabase.transaction(
+    idbDatabase.objectStoreNames,
+    'readwrite'
+  )
+  transaction.addEventListener('error', reject)
+
+  let count = 0
+  for (const storeName of idbDatabase.objectStoreNames) {
+    transaction
+      .objectStore(storeName)
+      .clear()
+      .addEventListener('success', () => {
+        count++
+        if (count === idbDatabase.objectStoreNames.length) {
+          // Cleared all object stores
+          resolve()
+        }
+      })
+  }
+}
diff --git a/readme.md b/readme.md
@@ -0,0 +1,56 @@
+# Back up and restore an IndexedDB database
+
+This gist is an [ES module](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules) which provides functions to import and export data from an [IndexedDB](https://developer.mozilla.org/en-US/docs/IndexedDB) database as JSON. It's based on Justin Emery's [`indexeddb-export-import`](https://github.com/Polarisation/indexeddb-export-import) package, but applies some adjustments that reflect better on the current browser landscape (i.e. better developer ergonomics but no support for Internet Explorer).
+
+## Usage
+For each of the provided functionalities, you need a connected [`IDBDatabase`](https://developer.mozilla.org/en-US/docs/Web/API/IDBDatabase) instance.
+
+### Export Data
+```js
+import { idb } from 'get-database-from-somewhere.js'
+
+import { exportToJson } from 'idb-backup-and-restore.js'
+
+exportToJson(idb)
+  .then(result => {
+    console.log('Exported JSON string:', result)
+  })
+  .catch(error => {
+    console.error('Something went wrong during export:', error)
+  })
+```
+
+### Import Data
+```js
+import { idb } from 'get-database-from-somewhere.js'
+import { serializedData } from 'get-serialized-data-from-somewhere.js'
+
+import { importFromJson } from 'idb-backup-and-restore.js'
+
+importFromJson(idb, serializedData)
+  .then(() => {
+    console.log('Successfully imported data')
+  })
+  .catch(error => {
+    console.error('Something went wrong during import:', error)
+  })
+```
+
+### Clear Database
+Depending on your use case, it can be reasonable to clear a database before importing serialized data:
+
+```js
+import { idb } from 'get-database-from-somewhere.js'
+import { serializedData } from 'get-serialized-data-from-somewhere.js'
+
+import { importFromJson, clearDatabase } from 'idb-backup-and-restore.js'
+
+clearDatabase(idb)
+  .then(() => importFromJson(idb, serializedData))
+  .then(() => {
+    console.log('Successfully cleared database and imported data')
+  })
+  .catch(error => {
+    console.error('Could not clear & import database:', error)
+  })
+```