HTML5 WebSql Database Migration

migrationManager.js

var migrationManager = (function() {

  /**
   * Our db instance
   * @type {Database}
   */
  var db = null;

  /**
   * Our versions, add a version when needed
   * @type {Array}
   */
  var versions = ['1.0', '1.1'];

  return {

    /**
     * Establish a db connection
     * @param {string} name of the database
     * @param {string} version number, you must use '' or null to work
     * @param {string} displayName self-describing right? ;)
     * @param {integer} size set to null, 0 or else
     */
    connect: function(name, version, displayName, size) {

      db = window.openDatabase(name, version || '', displayName, size || 0);

    },

    /**
     * Check if our db version is up2date
     */
    checkDb: function() {

      var fromVersionIndex = null;
      var currentVersion = db.version;
      var latestVersion = versions[versions.length - 1];

      // If we already have the lastest version,
      // bail out immediately
      if (currentVersion !== latestVersion) {

        // Check for empty version, meaning empty db
        if (currentVersion === '') {

          fromVersionIndex = 0;

        } else if (currentVersion !== '') {

          fromVersionIndex = versions.indexOf(currentVersion);

          if (fromVersionIndex === -1) {
            console.log("migrationManager Error: Can't locate version: " + currentVersion + " in versions stack: [" + versions.join(', ') + "]");
            return;
          }

          fromVersionIndex += 1;

        }

        // Change version from current to latest and run all the upgrades
        db.changeVersion(currentVersion, lastestVersion, function(transaction) {

          for (var i = fromVersionIndex; i < versions.length; i++) {
            this.upgradeDbToVersion(transaction, versions[i]);
          }

        }.bind(this));

      }
    },

    /**
     * Execute some SQL queries depending on requested version
     * @param {SQLTransaction} transaction object used to run queries
     * @param {string} version current upgrade version request
     */
    upgradeDbToVersion: function(transaction, version) {

     // Simple switch for running chunks of SQL Queries
      switch (version) {
        case '1.0':
          transaction.executeSql('CREATE TABLE "event" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "type" integer NOT NULL, "fullDate" text(30,0) NOT NULL);');
          break;
        case '1.1':
          transaction.executeSql('ALTER TABLE "event" ADD "name" text(255,0) NOT NULL;');
          break;
      }

    }
  }

})();