End Google Ads 201810 - BS.net 01 --> OK, my problem is...

I dont know how to hide a <div> when a dropdownlist change the index
I thought I can use ********** to solve this problem, but somehow... i dont know how to use it.

Here the code

TESTING












Choose div to be hide
Hide div1
Hide div2





When the user change the drop down into "Hide div2", the <div> with id div2 will hide which is style="DISPLAY: none"
How to use this thing like ********** where the page will not be ******* or postback