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var TDName = "TDFilter" .concat (Num); 
TDName.style.display = "block"; 
 
Why is my alert (TDName) displayed correctly, but it does n’t work when I use style? 
 
For example, my Num is 2, and after connecting, my TDName is TDFilter2, and I have this TD on my page, but why is the following sentence wrong? ? ? |   
 
 
 
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