Passing input paramters dynamically to Quey in BIRT report

Migrateduser

Hi All,
I have a requirement where I need to append the query dynamically based on the input parameters value.
I am trying the below method, but doesn't work

In DataSet open method

    testDataSet = MXReportDataSetProvider.create(this.getDataSource().getName(), this.getName());
    testDataSet.open();

    var sqlText = new String();

    sqlText = "  SELECT  id, status,job,site from workorder "

    + " where " + params["where"]
    + "siva"
    ;
maximoDataSet.setQuery(sqlText);

in beforeOpen method of Dataset I am trying replace the text siva **in the query dynamically based on input parameter, but it is giving error
**cannot call method 'replace of undefined". Please help me, how can I do it?

//beforeOpen code
sqlText = this.sqlText.replace("siva", "AND STATUS = " + params["site"]);

Thank you!!