I don’t think that currently we have a W3C standard to access to TPU.
Also the WIP webnn, in the current status, It is still limited to CPU/GPU devices:
https://www.w3.org/TR/webnn/#programming-model-device-selection 1
For Coral TPU that is a quite different use case see:

  
    
    
    TFJS and Coral TPU General Discussion
  
  
    This was the most updated status: