JavaScript and jQuery based backup and restore mechanism in JSON format.

backuprestorejson.js

// change to your database
var db = window.openDatabase("YourApp", "1.0.0", "DatabaseName", 5*1024); // 5*1024 is size in bytes

// file fail function
function failFile(error) {
 console.log("PhoneGap Plugin: FileSystem: Message: file does not exists, isn't writeable or isn't readable. Error code: " + error.code);
 alert('No backup is found, or backup is corrupt.');
}

// start backup (trigger this function with a button or a page load or something)
function startBackup() {
 navigator.notification.confirm('Do you want to start the backup? This will wipe your current backup. This action cannot be undone.', onConfirmBackup, 'Backup', 'Start,Cancel');
}

// backup confirmed
function onConfirmBackup(button) {
 if(button==1) {
  backupContent();
 }
}

// backup content
function backupContent() {
 db.transaction(
  function(transaction) {
   transaction.executeSql(
    // change this according to your table name
    'SELECT * FROM yourTable;', null,
    function (transaction, result) {
     if (result.rows.length > 0) {
      var tag = '{"items":[';
      for (var i=0; i < result.rows.length; i++) {
       var row = result.rows.item(i);
       // expand and change this according to your table attributes
       tag = tag + '{"attribute1":"' + row.attribute1 + '","attribute2":"' + row.attribute2 + '","attribute3":"' + row.attribute3 + '"}';
       if (i+1 < result.rows.length) {
        tag = tag + ',';
       }
      }
      tag = tag + ']}';
      window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function(fileSystem) {
       // Change the place where your backup will be written
       fileSystem.root.getFile("backup.txt", {create: true, exclusive: false}, function(fileEntry) {
        fileEntry.createWriter(function(writer) {
         writer.write(tag);
        }, failFile);
       }, failFile);
      }, failFile);
   alert("Backup done.");
     } else {
      alert("No content to backup.");
     }
    },
    errorHandlerSqlTransaction
   );
  }
 );
}

// start restore (trigger this function with a button or a page load or something)
function startRestore() {
 navigator.notification.confirm('Do you want to start the restore? This will wipe your current data. This action cannot be undone.', onConfirmRestore, 'Restore', 'Start,Cancel');
}

// restore confirmed
function onConfirmRestore(button) {
 if(button==1) {
  restoreContent();
 }
}

// restore content
function restoreContent() {
 db.transaction(
  function(transaction) {
   transaction.executeSql(
    // change this according to your table name
   'DELETE FROM yourTable', startRestoreContent()
  );
 });
}

// actually start restore content
function startRestoreContent() {
 window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function(fileSystem) {
  // Change the place where your backup is placed
  fileSystem.root.getFile("backup.txt", null, function(fileEntry) {
   fileEntry.file(function(file) {
    var reader = new FileReader();
    reader.onloadend = function(evt) {
     var data = JSON.parse(evt.target.result);
     var items = data.items;
     count = items.length;
     db.transaction(
      function(transaction) {
       $.each(items, function(index, item) {
        transaction.executeSql(
        // change and expand this according to your table name and attributes
        'INSERT INTO yourTable (attribute1, attribute2, attribute3) VALUES (?, ?, ?)',
        [item.attribute1, item.attribute2, item.attribute3],
        null
       );
      });
     });
    };
    reader.readAsText(file);
    alert("Restore done.");
   }, failFile);
  }, failFile);
 }, failFile);
}

// database sql transaction error message
function errorHandlerSqlTransaction(error) {
	console.error('SQLite - Error code: ' + error.code + ' - Error message: ' + error.message);
	return true;
}