Converting Code Behind VB to Javascript

Is there a way to convert the following to javascript.  Right now I am using the ListSearchExtender to select records in a dropdown, but I really would like the dropdown to actually be filtered and only show the records that match.  Any help would be appreciated.

Dim SelectStatement As String
        FromField = DropDownList2.SelectedValue
        Dim filedview As String = FromField & " LIKE '%" + SearchNew1.Text.Trim() + "%'"
        SqlDataSource9.FilterExpression = FromField & " LIKE '%" + SearchNew1.Text.Trim() + "%'"
        Me.SqlDataSource9.DataBind()