need to write javascript to display text based on a data field?

Migrateduser

<p>in my birt report there is a data field and a label field. In the report i need to check whether data field is having value 0. if the value ==0 then i have to display "****" in the label otherwise i have to display "yyy" in the label.</p>
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<p>where should i write the javascript and what shoulld i write to achieve this.</p>
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