Grabbing partial data from the clipboard in javascript

I have copied an Excel table which is about a million rows. When I look at the clipboard on my system, it seems to contain about 250MB of data. However, I only need to grab the styling information from it, for example:

This entire data comes out to (far) less than 1MB of data. Is there a way to read the clipboard as if it were a file or stream, so that I can just do, for example:

clipboard.read(1024)

Otherwise, if I do the straight:

evt.clipboardData.getData('text/html')

And grab the section of data I want after getting the data, it takes me over 10 seconds to do! Whereas I believe the event should only take 0.1s or so, if I'm able to read the clipboard data in a partial manner, as if it were a file.

What can I do here? Is it possible to use FileReader on the clipboard? If so, how could that be done?

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