Internet test with ping in NodeJS

ping-test-ifchanges-host.js

const ping = require('ping');

let host = '8.8.8.8';

if (process.argv[2]) {
	host = process.argv[2];
} else {
	console.log("Syntax: \nnode ping-test-ifchanges-host host");
}

console.log("Testing host: " + host);

let isAlivePrev = false;
let nowPrev = new Date();

function doPing() {
	ping.sys.probe(host, isAlive => {
		if (isAlive !== isAlivePrev) {
			let now = new Date();
			let diff = (now.getTime() - nowPrev.getTime())/1000;
			let timestamp = now.toISOString() + ' after: ' + diff + ' s';
			console.log("\n" + host + ': ' + (isAlive ? ' OK' : ' KO') + ' ' + timestamp);
			isAlivePrev = isAlive;
			nowPrev = now;
		} else {
			process.stdout.write('.');
		}
	});
}

setInterval(doPing, 1000);