前端：ajax访问时要加上“xhrFields: {withCredentials: true}” ，实现session可以传递
后端：Access-Control-Allow-Credentials 设置为 true；同时 Access-Control-Allow-Origin 必须指定 url
npm 安装 express、body-parser、express-session、svg-captcha
后台代码：
1 var express = require(‘express‘); 2 var app = express(); 3 var svgCaptcha = require(‘svg-captcha‘); // 动态验证码 4 var session = require(‘express-session‘); 5 var bodyParser = require(‘body-parser‘); // Express框架请求体解析的中间件 6 ?7 var urlencodedParser = bodyParser.urlencoded({ extended: false }); 8 ?9 app.use(session({10 ??resave: true, // don‘t save session if unmodified11 ??saveUninitialized: false, // don‘t create session until something stored12 ??secret: ‘node‘13 }));14 app.use(function (req, res, next) {15 ??// Website you wish to allow to connect16 ??res.setHeader(‘Access-Control-Allow-Origin‘, req.headers.origin);17 ??// res.setHeader(‘Access-Control-Allow-Origin‘, "*");18 19 ??// Request methods you wish to allow20 ??res.setHeader(‘Access-Control-Allow-Methods‘, ‘GET, POST, OPTIONS, PUT, PATCH, DELETE‘);21 22 ??// Request headers you wish to allow23 ??res.setHeader(‘Access-Control-Allow-Headers‘, ‘X-Requested-With,content-type‘);24 25 ??// Set to true if you need the website to include cookies in the requests sent26 ??// to the API (e.g. in case you use sessions)27 ??res.setHeader(‘Access-Control-Allow-Credentials‘, true);28 29 ??// Pass to next layer of middleware30 ??next();31 });32 33 34 app.get(‘/‘, function (req, res) {35 ??res.send(‘Hello World‘);36 });37 app.post(‘/trendsCode‘, urlencodedParser, function (req, res) { 38 ??var code = req.body.code;39 ??if (code) {40 ????var response = {41 ??????msg: ‘success‘,42 ??????trendsCode: req.session.trendsCode43 ????};44 ????res.send(JSON.stringify(response));45 ??} else {46 ????var codeConfig = {47 ??????size: 5, // 验证码长度48 ??????noise: 2, // 干扰线条的数量49 ??????height: 4450 ????}51 ????var captcha = svgCaptcha.create(codeConfig);52 ????req.session.trendsCode = captcha.text;53 ????res.send(captcha.data);54 ??}55 });56 57 var server = app.listen(8080, function () {58 ??var host = server.address().address59 ??var port = server.address().port60 61 ??console.log("应用实例，访问地址为 http://%s:%s", host, port);62 });前端代码：
1 <!DOCTYPE html> 2 <html lang="en"> 3 ?4 <head> 5 ??<meta charset="UTF-8"> 6 ??<meta name="viewport" content="width=device-width, initial-scale=1.0"> 7 ??<meta http-equiv="X-UA-Compatible" content="ie=edge"> 8 ??<title>ajax 跨域 session 传值</title> 9 </head>10 11 <body>12 ??<h1>trends code</h1>13 ??<div id="code"></div>14 ??<input type="text" id="input">15 ??<input type="button" value="提交" onclick="submit()">16 17 ??<script src="./jquery-3.3.1.min.js"></script>18 ??<script>19 ????window.onload = function () {20 ??????$.ajax({21 ????????url: "http://127.0.0.1:8080/trendsCode",22 ????????type: ‘POST‘,23 ????????xhrFields: {24 ??????????withCredentials: true25 ????????},26 ????????success: function (response) {27 ??????????// console.log(‘response--‘,response);28 ??????????$(‘#code‘).html(response);29 ????????},30 ????????error: function (error) {31 ??????????console.log(‘error--‘, error)32 ????????}33 ??????});34 ????};35 ????var submit = function () {36 ??????// console.log(‘submit‘);37 ??????var inputCode = $(‘#input‘).val();38 ??????$.ajax({39 ????????url: "http://127.0.0.1:8080/trendsCode",40 ????????data: {41 ??????????code: inputCode42 ????????},43 ????????type: ‘POST‘,44 ????????xhrFields: {45 ??????????withCredentials: true46 ????????},47 ????????success: function (response) {48 ??????????console.log(‘response--‘, response);49 ??????????// document.write(response);50 ????????},51 ????????error: function (error) {52 ??????????console.log(‘error--‘, error)53 ????????}54 ??????});55 ????};56 ??</script>57 </body>58 59 </html>前端 xhrFields 的设置（XMLHttpRequest 和 jquery）
1 // XMLHttpRequest 2 var xhr = new XMLHttpRequest(); 3 xhr.open(‘GET‘, ‘http://127.0.0.1:8080/trendsCode‘); 4 xhr.withCredentials = true; 5 xhr.onload = onLoadHandler; 6 xhr.send(); 7 ?8 // jquery 9 $.ajax({10 ????url: "http://127.0.0.1:8080/trendsCode",11 ????type: "GET",12 ????xhrFields: {13 ????????withCredentials: true14 ????},15 ????success: function (data) {16 ????????// do something17 ????}18 });参考文章： https://blog.csdn.net/jiahao791869610/article/details/79175268
前后端分离 ajax 跨域 session 传值 （后端使用 node）
原文地址：https://www.cnblogs.com/landmass/p/9876842.html