Can I use walletnotify or blocknotify remotely with a NodeJS application? I'd like to get information from my bitcoin node running on a cloud server to be used to make changes in my NodeJS app running on my computer. So, in the bitcoin.conf file, should I have something like walletnotify=curl http://My.IP.Address:PortAppUses/walletnotify.js?tx=%s? If that's right, what do I write in the walletnotify.js file to simply save the incoming transaction id as a variable?
In your example you are telling it to place the transaction id as a GET request in the URI under the tx parameter. 

walletnotify=curl http://My.IP.Address:PortAppUses/walletnotify.js?tx=%s


All you would need to do inside of walletnotify.js is pull the tx GET, in nodejs express that would be something like:

const express = require("express");
const app = express();
const request = require("request");

app.get("/", function(req, res){

    let transactionId = req.query.tx;

    //do whatever with transactionId

});