website/static/workers/flight-path-data-decoder.js

importScripts('./util.js');
const FLUSH_LIMIT = 20000;
let result = [];
let index = 0;
let count = 0;

onmessage = function(e) {
  const lines = e.data.text.split('\n');

  lines.forEach(function(line) {

    if (!line) {
      return;
    }

    var parts = line.split('\t');
    var coords0 = parts[2].split('\x01').map(function(str) { return decodePolyline(str, 5) });
    var coords1 = parts[3].split('\x01').map(function(str) { return decodePolyline(str, 1) });

    coords0.forEach(function(lineStr, i) {
      for (var j = 1; j < lineStr.length; j++) {
        var prevPt0 = coords0[i][j - 1],
            prevPt1 = coords1[i][j - 1],
            currPt0 = coords0[i][j],
            currPt1 = coords1[i][j];

        result.push({
          name: parts[0],
          country: parts[1],
          start: [prevPt0[0], prevPt0[1], prevPt1[0]],
          end: [currPt0[0], currPt0[1], currPt1[0]]
        });
        count++;
      }
    });

    if (result.length >= FLUSH_LIMIT) {
      flush();
    }
  });

  if (e.data.event === 'load') {
    flush();
    postMessage({action: 'end'});
  }
};

function flush() {
  postMessage({
    action: 'add',
    data: result,
    meta: {count}
  });
  result = [];
}