Google Polyline Encoder

encode.js

function encode(locations) {
  var lastLat = 0.0;
  var lastLng = 0.0;

  var result = "";

  for (i in locations) {
    var location = locations[i];
    var lat = Math.round(location[1] * 1e5);
    var lng = Math.round(location[0] * 1e5);

    var dLat = lat - lastLat;
    var dLng = lng - lastLng;

    result += encodeCoordinate(dLat);
    result += encodeCoordinate(dLng);

    lastLat = lat;
    lastLng = lng;
  }

  return result;
}

function encodeCoordinate(coord) {
  var result = "";

  coord = coord << 1;
  if (coord < 0) {
    coord = ~coord;
  }
  while (coord >= 0x20) {
    result += String.fromCodePoint((0x20 | (coord & 0x1F)) + 63);
    coord = coord >> 5;
  }

  result += String.fromCodePoint(coord + 63);

  return result;
}