Convert coords from Google Maps (WGS-84) to Baidu Maps (BD-09)

gistfile1.js

/**
 * Convert longitude and latitude from standard WGS-84 system
 * to Baidu's BD-09
 * 
 * @see http://stackoverflow.com/a/29512814/718811 for a detailed
 * description of the problem.
 * 
 * @param float lng Longitude
 * @param float lat Latitude
 * @return object Converted coords
 */
function convertCoords(lng, lat){
    var x_pi = 3.14159265358979324 * 3000.0 / 180.0;
    var x = lng, y = lat;
    var z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
    var theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);
    var bd_lon = z * Math.cos(theta) + 0.0065;
    var bd_lat = z * Math.sin(theta) + 0.006;
    return {lng: bd_lon, lat:bd_lat};
};