How to use spi to write and read some specfic register address

What is being used as the trigger to fetch the data? Is it the movement of the device, or is it human input, via a switch perhaps?

'I think this is possible. but if this is true, wouldn't it make it very hard to pull the data in high frequency?'

Your data posts, show that it is possible to fetch data reliably at 4 msec 0.004 as the timing is around 0.003+ and that seems a good value based on other devices I have used. So, is 200+ samples per second what is needed in your design? It certainly seems doable, and my gut feel is that the Javascript engine will be able to keep up at that demand. What isn't clear is what is needed in the design.

1 / 833 = 0.0012 in msec
At that frequency, My understanding is that the FIFO will fill up faster than it is possible to fetch the data (0.003+) Have you tried a slower update frequency? Have you considered inline 'C ' to speed up execution?

http://www.espruino.com/InlineC

While anything goes, aren't accelerometers polled at say a tenth second interval, then acted upon when that duration is exceeded?