Answers for "header("Access-Control-Allow-Origin: *");"

access-control-allow-origin

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "X-Requested-With");
  next();
  });

allow cross origin

Access-Control-Allow-Origin: *
Access-Control-Allow-Origin: <origin>
Access-Control-Allow-Origin: null

cross origin even with allow header

header('Access-Control-Allow-Origin: http://localhost:8100');
header ("Access-Control-Expose-Headers: Content-Length, X-JSON");
header ("Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS");
header ("Access-Control-Allow-Headers: Content-Type, Authorization, Accept, Accept-Language, X-Authorization");
header('Access-Control-Max-Age: 86400');

if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    // The request is using the POST method
    header("HTTP/1.1 200 OK");
    return;

}

header access-control particular domain

Access-Control-Allow-Origin: http://siteA.com

set Access-Control-Allow-Origin header to * cors

var config = {
development: {
    //url to be used in link generation
    url: 'http://my.site.com',
    //mongodb connection settings
    database: {
        host:   '127.0.0.1',
        port:   '27017',
        db:     'site_dev'
    },
    //server details
    server: {
        host: '127.0.0.1',
        port: '3422'
    }
},
production: {
    //url to be used in link generation
    url: 'http://my.site.com',
    //mongodb connection settings
    database: {
        host: '127.0.0.1',
        port: '27017',
        db:     'site'
    },
    //server details
    server: {
        host:   '127.0.0.1',
        port:   '3421'
    }
}
};
module.exports = config;