Why do you wanna add this from Javascript? If you are embedding Windows Media Player Object in WebPage, all buttons (play,pause,stop and etc) are already included in that object. So, I don't think you need to add this duplicated features from Javascript.. You can check the screenshot here.
<embed type="application/x-mplayer2" pluginspage="http://www.microsoft.com/Windows/MediaPlayer/" name="mediaplayer1" ShowStatusBar="true" EnableContextMenu="false" autostart="false" width="320" height="240" loop="false" src="MyVideo.wmv" />
Ref: Embedding Windows Media Player into a web page
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