JavasScript is case sensitive, so is the IndexedDB. You can use option - 'IgnoreCase' to filter records with case insensitive.

connection.select({
    from: "Table_Name",
    ignoreCase: true,
    where: {
        Column1: some_value,
        Column2: some_another_value
    }
}).then(function(results) {
    //results will be array of objects.
    console.log(results);
}).catch(function(error) {
    alert(error.message);
});

Example