JAVASCRIPT

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

cors Access-Control-Allow-Origin cor

// Add headers
app.use(function (req, res, next) {

    // Website you wish to allow to connect
    res.setHeader('Access-Control-Allow-Origin', 'http://localhost:8888');

    // Request methods you wish to allow
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');

    // Request headers you wish to allow
    res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');

    // Set to true if you need the website to include cookies in the requests sent
    // to the API (e.g. in case you use sessions)
    res.setHeader('Access-Control-Allow-Credentials', true);

    // Pass to next layer of middleware
    next();
});

implement 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 cors access-control-allow-origin

fetch('https://cortex.fun', {mode: 'no-cors'}) // >> {mode: 'no-cors'} <<
.then(res => res.json())
.then(data => console.log(data))

Access-Control-Allow-Origin

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

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;

Add Access-Control-Allow-Origin html

<?php
header("Access-Control-Allow-Origin: *");
...
?>