Getting an error using indexOf call in Javascript on Firefox and Opera. Works fine in IE.

Following is the error message:

Action

function anonymous(Grid, Row, Col, Event) { 

    return Grid.ActionShowPopupMenu(); 

} 

for event OnRightClick failed with exception: row.id.indexOf is not a function

I'm testing that a string contains another string in Javascript and using the indexOf function of a string. The calls however are being made in JQuery functions. Perhaps that is the reason for the problem? Is there an alternative to using indexOf in Javascript to test if a string contains another string? Is there a workaround for this problem?