app/index.html

<html>
<head>
<title>updater</title>
</head>
<body>
<div id="version"></div>
<div id="loaded"></div>
<script>
  var gui = require('nw.gui');
  var copyPath, execPath;
  if(gui.App.argv.length){
    copyPath = gui.App.argv[0];
    execPath = gui.App.argv[1];
  }


  //download new version of app in tmp
  //unpack
  //run updater
  //updater will copy itself to origin directory
  //updater will run app
  var pkg = require('./package.json');
  var axios = require('axios');
  var url = require('url');
  var path = require('path');
  var os = require('os');
  var fs = require('fs');
  var k = 0;
  var d = false;
  var updater = require('./updater.js');
  var upd = new updater(pkg);
  var newVersionCheckIntervalId = null;
  var tryingForNewVersion = false;
  
  //for test purposes
  
  
  if(!copyPath){
    axios.get(url.resolve(pkg.manifestUrl, '/version/'+ pkg.version));
    document.getElementById('version').innerHTML = 'current version ' + pkg.version;
    newVersionCheckIntervalId = setInterval(function(){
      if(!d && !tryingForNewVersion) {
          tryingForNewVersion = true; //lock
          upd.checkNewVersion(versionChecked);
      }
    }, 500);
  } else {
    document.getElementById('version').innerHTML = 'copying app';
    upd.install(copyPath, newAppInstalled);
    
    function newAppInstalled(err){
      if(err){
        console.log(err);
        return;
      }
      upd.run(execPath, null);
      gui.App.quit();
    }
  }

  function versionChecked(err, newVersionExists, manifest){
    tryingForNewVersion = false; //unlock
    if(err){
        console.log(err);
        return Error(err);
    }
    else if(d){
        console.log('Already downloading');
        return;
    }
    else if(!newVersionExists){
        console.log('No new version exists');
        return;
    }
    d = true;
    clearInterval(newVersionCheckIntervalId);
    var loaded = 0;
    var newVersion = upd.download(function(error, filename){
        newVersionDownloaded(error, filename, manifest);
    }, manifest);

    newVersion.on('data', function(chunk){
      loaded+=chunk.length;
      document.getElementById('loaded').innerHTML = "New version loading " + Math.floor(loaded / newVersion['content-length'] * 100) + '%';
    })
  }

  function newVersionDownloaded(err, filename, manifest){
    if(err){
      console.log(err)
      return Error(err);
    }
    document.getElementById('loaded').innerHTML = "unpacking: " + filename;
    upd.unpack(filename, newVersionUnpacked, manifest);
  }

  function newVersionUnpacked(err, newAppPath){
    if(err){
      console.log(err)
      return Error(err);
    }
    var runner = upd.runInstaller(newAppPath, [upd.getAppPath(), upd.getAppExec()]);
    gui.App.quit();
  }


</script>
</body>
</html>