How to detect if a placement would be empty (Doubleclick for Publishers)?

Question

I want to use DFP for my ads. To display an ad I am calling GA_googleFillSlot(). My understanding of this is, that this function injects the ad code at the position where the JS call is placed. How can I detect if the placement is empty, e.g. no banner code will be injected because there is currently no banner. I need to know because the surrounding html needs to be adapted. Any ideas?

Edit:
Alternatively, is it possible to alter the injected html elements? DFP injects a div with id="google_ads_div_$PLACEMENT_ID">. Is it possible to add a class attribute?

Answer 1

Using JavaScript, you can use the .innerHTML attribute to see if there is any HTML inside of the div after the GA_googleFillSlot().

And yes, the div tag supports both id and class attributes: click.

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