Ping a Server in Javascript. Uses but does not need AngularJS 1.4.x

var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope) {
  $scope.model = {
    pingState: 'unsent'
  };

  // Presuming a server running locally at port 8080
  ping('localhost:8080/!none.png', function callback (response, e) {
    $scope.model.pingState = response;
    console.log(response);
    console.log(e);
    $scope.$apply();
  });

  function ping(ip, callback) { // via http://jsfiddle.net/GSSCD/203/
    if (!this.inUse) {
      this.status = 'unchecked';
      this.inUse = true;
      this.callback = callback;
      this.ip = ip;
      var _that = this;
      this.img = new Image();
      this.img.onload = function () {
        _that.inUse = false;
        _that.callback('responded');

      };
      this.img.onerror = function (e) {
        if (_that.inUse) {
          _that.inUse = false;
          _that.callback('error', e);
        }

      };
      this.start = new Date().getTime();
      this.img.src = "http://" + ip;
      this.timer = setTimeout(function () {
        if (_that.inUse) {
          _that.inUse = false;
          _that.callback('timeout');
        }
      }, 1500);
    }
  }
});

<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <script data-require="angular.js@1.4.x" src="https://code.angularjs.org/1.4.12/angular.js" data-semver="1.4.9"></script>
    <script data-require="jquery@*" data-semver="3.0.0" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.0.0/jquery.js"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <p>Ping Status: {{model.pingState}}</p>
    <div style="background-color:red; width:128px; height:128px;" ng-if="model.pingState != 'responded'"></div>
    <div style="background-color:green; width:128px; height:128px;" ng-if="model.pingState == 'responded'"></div>
  </body>

</html>