javascript passing string parameter

I need to pass a string parameter as a second parameter for my action result.

public ActionResult AvaliarPrevia(int Id, String Tipo)

but when I try this, the second parameter remains null.

let a = '<a href=AvaliarPrevia/' + row.Id + '?' + row.OrcamentoTipo + ' title="Avaliar" class ="btn btn-info btn-sm"><i class="fa fa-check-square-o"></i></a>';