filterCities.js

var fs = require('fs');
var cities = [];
var underscore = require("underscore");

var data = fs.readFileSync("public/retailers.json", "utf-8", function(result, error) {
  if(!error) {
    return result;
  }
});

data = JSON.parse(data);
for(var i in data) {
  var uniqueCities;
  cities.push(data[i].city);
}

var uniqueCities = underscore.unique(cities);
var sortedCities = underscore.unique(uniqueCities);

var file = fs.createWriteStream('cities.txt');
file.on("error", function(err) {
  throw err;
});

fs.writeFile("cities.json", JSON.stringify(sortedCities), function(err) {
  if(err) {
    console.log(err);
  }
  else {
    console.log("File saved");
  }
});