解决NodeJS+Express模块的跨域访问控制问题：Access-Control-Allow-Origin

在一个项目上想用NodeJS，所以边学边练。第一个遇到的问题就是跨域访问控制问题。很多初学者会遇到同样问题。

问题

在前端的JS（http://localhost/xxx）中ajax访问后端RestAPI(http://localhost:3000/….)时(Chrome)报错：

XMLHttpRequest cannot load http://localhost:3000/auth/xxx/xxx. Origin http://localhost is not allowed by Access-Control-Allow-Origin.

方案

解决代码如下：

var express = require('express');
var app = express();
//设置跨域访问
app.all('*', function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "X-Requested-With");
    res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");
    res.header("X-Powered-By",' 3.2.1')
    res.header("Content-Type", "application/json;charset=utf-8");
    next();
});

app.get('/auth/:id/:password', function(req, res) {
    res.send({id:req.params.id, name: req.params.password});
});

app.listen(3000);
console.log('Listening on port 3000...');