Why does NWJS fire twice?

Question

Node.js

I use the editor from Microsoft
Addition https://marketplace.visualstudio.com/items?itemNam...
package.json:

{
  "main": "assets/index.html",
  "name": "AlkahCraft",
  "version": "0.1",
  "window": {
    "icon": "assets/img/icon.png",
    "title": "AlkahCraft",
    "toolbar": false,
    "width": 800,
    "height": 500,
    "frame": false,
    "resizable": false
  },
  "webkit": {
    "page-cache": true,
    "plugin": false
  }
}

in index.html added text: and it worked twice why ?
alert("gg")