Supply a default file extension in the save dialog

[briandk]

var fs = require('fs'); // require only if you don't already have it

function saveFile () {
  dialog.showSaveDialog({ filters: [
     { name: 'text', extensions: ['txt'] } //  this is where the magic happens 
    ]}, function (fileName) {
    if (fileName === undefined) return;
    fs.writeFile(fileName, document.getElementById("editor").value, function (err) {   
    });
  }); 
}