HTML5 Promise-based WebSQL query convenience-function

easysql.js

// https://github.com/Philzen/WebSQL-Polyfill
// https://github.com/jakearchibald/es6-promise

/**
 * Usage:
 * var db = new DB('demo', '1.0', 'Demo', 2 * 1024 * 1024);
 * db.query('SELECT * FROM mytable')
 *   .then(function(res){
 *     console.log(res.rows); 
 *   }, function(err){
 *     console.error(err);
 *   });
 * 
 */

function DB(name, version, title, size){
  this.db = openDatabase(name, version, title, size);
}

DB.prototype.query = function(sql, params){
  var db = this.db;
  return new Promise(function(resolve, reject){
    if (!db) return reject('no database.');
    db.transaction(function(tx){
      tx.executeSql(sql, params||[], function(tx,res){
        // tidy up
        var rows = [];
        for(var i=res.rows.length; i; i--){
          rows.unshift(res.rows.item(i-1));
        }
        var out = {rows:rows, rowsAffected:res.rowsAffected};
        // don't worry about no insertId
        try{ out.insertId = res.insertId; }catch(e){}
        resolve(out);
      }, function(tx, err){
        reject(err.message);
      });
    });
  });
};