Polyline JavaScript Module

polyline.js

var polyline = {};

polyline.encodeCoordinate = function(coordinate) {
    coordinate = Math.round(1e5 * coordinate);
    coordinate <<= 1;
    0 > coordinate && (coordinate = ~coordinate);
    var output = "";
    while (coordinate >= 32) {
        output += String.fromCharCode((32 | 31 & coordinate) + 63);
        coordinate >>= 5;
    }
    output += String.fromCharCode(coordinate + 63);
    return output;
};

polyline.decodeCoordinate = function(str) {
    for (var i = 0; i < str.length; i++) {
        {
            str.charCodeAt(i) - 63;
        }
        result |= (31 & b) << shift;
        shift += 5;
    }
};

polyline.decodeLine = function(str) {
    var latitude_change, longitude_change, index = 0, lat = 0, lng = 0, coordinates = [], shift = 0, result = 0, byte = null;
    while (index < str.length) {
        byte = null;
        shift = 0;
        result = 0;
        do {
            byte = str.charCodeAt(index++) - 63;
            result |= (31 & byte) << shift;
            shift += 5;
        } while (byte >= 32);
        latitude_change = 1 & result ? ~(result >> 1) : result >> 1;
        shift = result = 0;
        do {
            byte = str.charCodeAt(index++) - 63;
            result |= (31 & byte) << shift;
            shift += 5;
        } while (byte >= 32);
        longitude_change = 1 & result ? ~(result >> 1) : result >> 1;
        lat += latitude_change;
        lng += longitude_change;
        var precision = Math.pow(10, -5);
        coordinates.push({
            latitude: lat * precision,
            longitude: lng * precision
        });
    }
    return coordinates;
};

polyline.encodePoint = function(x, y) {
    return this.encodeCoordinate(x) + this.encodeCoordinate(y);
};

polyline.encodeLine = function(coordinates) {
    var output = "", longitude = 0, latitude = 0;
    for (var i = 0; i < coordinates.length; i++) {
        var pt = [ coordinates[i][0], coordinates[i][1] ];
        (latitude || longitude) && (pt = [ pt[0] - latitude, pt[1] - longitude ]);
        output += this.encodePoint(pt[0], pt[1]);
        latitude = pt[0];
        longitude = pt[1];
    }
    return output;
};

void 0 !== typeof module && (module.exports = polyline);