Detect Snowplow

forecast.js

var page = require('webpage').create();
var system = require('system');
if (system.args.length === 1) {
  console.log('Usage: you must provide some URL to check');
  phantom.exit();
}
page.open(system.args[1], function(status) {
  var usesSnowplow;
  var information;
  if(status === "success") {
    var answer = page.evaluate(function(){
      return window.GlobalSnowplowNamespace !== undefined || window._snaq !== undefined;
    });
    usesSnowplow = answer;
    information = usesSnowplow ? "YES" : "NO";
  } else {
    information = "UNKNOWN";
  }
  console.log(system.args[1] + " : " + information);
  phantom.exit();
});

First install phantomJS.

Then run

➜  phantomjs forecast.js http://snowplowanalytics.com
http://snowplowanalytics.com : YES

Output is YES if the site does have Snowplow, NO if it doesn't, and UNKNOWN if the connection failed.