Chunk OpenWeatherMap city list.

gistfile1.js

var fs = require('fs')
var rawData = JSON.parse(fs.readFileSync('city.list.json', 'utf8'))

var formatedData = {}

rawData.forEach(function(city){
    var country = city.country

    if (!(country in formatedData)){
        formatedData[country] = {}
        formatedData[country].cities = {}
    }

    formatedData[country].cities[city._id] = city.name
});

Object.keys(formatedData).forEach(function(countryCode){
    var country = formatedData[countryCode]

    fs.writeFileSync("/tmp/data/" + countryCode + ".json", JSON.stringify(country.cities));
});