On OSX and Windows , there are multiple types of clipboards for different types of content. When you copy content in Excel, data is stored in the plaintext and in the html clipboard.
The right way (that doesn't get tripped up by delimiter issues) is to parse the HTML. http://jsbin.com/uwuvan/5 is a simple demo that shows how to get the HTML clipboard. The key is to bind to the onpaste event and read
event.clipboardData.getData('text/html')