There is a few YouTube video on node.js for bitcoin...not too sure how much it will help u though
What exactly are u trying to do?
I would look up the node.js github page and see what the equivalent is for getblockhash...like I said I am pretty sure you have to get the format or template first then get the last blockhash ...
U could try getblocktemplate(TX id)
If you are trying to get the block hash containing a transaction...
In core wallet its decodetransaction (TX id)
And that returns the block hash the transaction is in