reduce.js

// usage
// node reduce.js worldmap.geojson 3

var fs = require('fs')

var json_string = fs.readFileSync(process.argv[2])
var precision = parseInt(process.argv[3])

console.log('original length: ' + json_string.length)

var obj = JSON.parse(json_string)

var n_found = 0

iterate(obj)

function iterate(o) {

  for (var key in o) {
    if (typeof o[key] === 'object') {
      iterate(o[key])
    } else {
      if (typeof o[key] === 'number') {
        n_found += 1
        o[key] = +o[key].toFixed(precision)
      }
    }
  }

}

console.log('numbers found: ', n_found)
console.log('reduced length: ' + JSON.stringify(obj, null, 0).length)

var pct = 1.0 - (JSON.stringify(obj, null, 0).length / json_string.length)

fs.writeFileSync(process.argv[2] + '.reduced.json', JSON.stringify(obj, null, 0))

console.log((pct * 100.0).toFixed(2) + '% reduction')

worldmap.geojson

worldmap.geojson.reduced.geojson