Check if index exists in WebSQL

Is there a way to check if an index exists for a table in WebSQL database? I'm using CREATE UNIQUE INDEX INDEX_GUID ON TABLE PERSONS for creation. But if index already exists I get an error:

{
    code: 5, // SYNTAX_ERR - from docs
    message: "could not prepare statement (1 index INDEX_GUID already exists)"
}

The best solution for me would be to list all indexes of a table.

I am using this but it's a workaround. I hope that error messages are allways in english.

db.transaction(function (tx) {
    tx.executeSql(
        "CREATE UNIQUE INDEX INDEX_GUID ON TABLE PERSONS",
        [],
        function (tx, rs) {
            // index created
        },
        function (tx, e) {
            if (e.message.indexOf("already exists") == -1) {
                // index not created - already exists
            }
        });
    );
});