shapefile to geojson

index.js

const stream = require('stream');
const fs = require('fs');

const unzip = require('unzip-stream');
const Zip2GeoJsonStream = require('./zip2geojson');

const file = process.argv[2];

const readStream = fs
  .createReadStream(file)
  .pipe(unzip.Parse())
  .pipe(new Zip2GeoJsonStream())
  .pipe(fs.createWriteStream(file.replace(/\.[^\.]+$/, '.geojson')));

package.json

{
  "devDependencies": {},
  "dependencies": {
    "event-stream": "^3.3.4",
    "project-geojson": "^1.0.2",
    "shapefile": "^0.6.6",
    "unzip-stream": "^0.2.1"
  }
}

zip2geojson.js

const fs = require('fs');
const path = require('path');
const stream = require('stream');

const es = require('event-stream');
const project = require('project-geojson');
const shapefile = require('shapefile');

const EXTENSIONS = ['.prj', '.shp', '.dbf'];

class Shp2GeoJSONStream extends stream.Readable {
  constructor(shp, dbf) {
    super({ objectMode: true });
    this.source = shapefile.open(shp, dbf);
  }

  _read() {
    this.source.then(source => {
      source.read().then(result => {
        this.push(result.done ? null : result.value);
      });
    });
  }
}

class Zip2GeoJsonStream extends stream.Transform {
  constructor() {
    super({ objectMode: true });
    this.buffers = {};
  }

  _transform(entry, e, cb) {
    const filename = entry.path;
    const extname = path.extname(filename);

    if (EXTENSIONS.indexOf(extname) > -1) {
      entry.pipe(
        es.wait((err, buff) => {
          this.buffers[extname] = buff;
          cb();
        })
      );

      return;
    }

    entry.autodrain();
    cb();
  }

  _flush(cb) {
    let dataStream = null;
    let projStream = es.through();

    // handle shp/dbf files
    if ('.shp' in this.buffers) {
      const shpBuff = this.buffers['.shp'];
      const dbfBuff = this.buffers['.dbf'];
      dataStream = new Shp2GeoJSONStream(shpBuff, dbfBuff);
    }

    // handle projection files
    if ('.prj' in this.buffers) {
      const prjBuff = this.buffers['.prj'];
      projStream = project.obj(prjBuff.toString(), 'EPSG:4326');
    }

    if (!dataStream) {
      throw new Error(
        'provided zip file does not contain valid shape or vector files'
      );
    }

    // pipe the data to the projection stream and then push each record to the
    // next part of the stream using a pass-through stream
    dataStream.pipe(projStream);
    // .pipe(es.through(record => this.push(record), () => cb()));
    cb();
  }
}

module.exports = Zip2GeoJsonStream;