浅谈跨域-就你小子不让我跨域

var script = document.createElement('script');
  script.type = 'text/javascript';

  // 传参一个回调函数名给后端，方便后端返回时执行这个在前端定义的回调函数
  script.src = 'http://www.domain2.com:8080/login?user=admin&callback=handleCallback';
  document.head.appendChild(script);

  // 回调执行函数
  function handleCallback(res) {
      alert(JSON.stringify(res));
  }

$.ajax({
  url: 'http://www.domain2.com:8080/login',
  type: 'get',
  dataType: 'jsonp',  // 请求方式为jsonp
  jsonpCallback: "handleCallback",  // 自定义回调函数名
  data: {}
});

this.$http = axios;
this.$http.jsonp('http://www.domain2.com:8080/login', {
  params: {},
  jsonp: 'handleCallback'
  }).then((res) => {
  console.log(res);
})

var querystring = require('querystring');
var http = require('http');
var server = http.createServer();
server.on('request', function(req, res) {
  var params = querystring.parse(req.url.split('?')[1]);
  var fn = params.callback;
  // jsonp返回设置
  res.writeHead(200, { 'Content-Type': 'text/javascript' });
  res.write(fn + '(' + JSON.stringify(params) + ')');
  res.end();
});
server.listen('8080');
console.log('Server is running at port 8080...');

var xhr = new XMLHttpRequest(); // IE8/9需用window.XDomainRequest兼容

// 前端设置是否带cookie
xhr.withCredentials = true;

xhr.open('post', 'http://www.domain2.com:8080/login', true);
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xhr.send('user=admin');

xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
        alert(xhr.responseText);
    }
};

$.ajax({
...
xhrFields: {
    withCredentials: true    // 前端设置是否带cookie
},
crossDomain: true,   // 会让请求头中包含跨域的额外信息，但不会含cookie
...
});

var http = require('http');
var server = http.createServer();
var qs = require('querystring');

server.on('request', function(req, res) {
    var postData = '';
    // 数据块接收中
    req.addListener('data', function(chunk) {
        postData += chunk;
    });
    // 数据接收完毕
    req.addListener('end', function() {
        postData = qs.parse(postData);

        // 跨域后台设置
        res.writeHead(200, {
            'Access-Control-Allow-Credentials': 'true',     // 后端允许发送Cookie
            'Access-Control-Allow-Origin': 'http://www.domain1.com',    // 允许访问的域（协议+域名+端口）
            /* 
             * 此处设置的cookie还是domain2的而非domain1，因为后端也不能跨域写cookie(nginx反向代{过}{滤}理可以实现)，
             * 但只要domain2中写入一次cookie认证，后面的跨域接口都能从domain2中获取cookie，从而实现所有的接口都能跨域访问
             */
            'Set-Cookie': 'l=a123456;Path=/;Domain=www.domain2.com;HttpOnly'  // HttpOnly的作用是让js无法读取cookie
        });

        res.write(JSON.stringify(postData));
        res.end();
    });
});
server.listen('8080');
console.log('Server is running at port 8080...');

fetch('http://localhost:6888/test_get',{
    method: 'GET',
    mode: 'cors',
}).then(res => {
    return res.json();
}).then(json => {
    console.log('获取的结果', json.data);
    return json;
}).catch(err => {
    console.log('请求错误', err);
})

fetch('http://localhost:6888/test_post',{
    method: 'POST',
    body: JSON.stringify({name: 'zaozuo'}),
    mode: 'cors',
}).then(res => {
    return res.json();
}).then(json => {
    console.log('获取的结果', json.data);
    return json;
}).catch(err => {
    console.log('请求错误', err);
})

var http = require('http');
var socket = require('socket.io');

// 启http服务
var server = http.createServer(function(req, res) {
    res.writeHead(200, {
        'Content-type': 'text/html'
    });
    res.end();
});

server.listen('8080');
console.log('Server is running at port 8080...');

// 监听socket连接
socket.listen(server).on('connection', function(client) {
    // 接收信息
    client.on('message', function(msg) {
        client.send('hello：' + msg);
        console.log('data from client: ---> ' + msg);
    });

    // 断开处理
    client.on('disconnect', function() {
        console.log('Client socket has closed.'); 
    });
});