nodejs express 设置跨域

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引入express，并设置header头部信息

提醒：一定要先加代码，然后再引用api

var app = express();
//先加头部信息
app.all('*', function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");//允许所有来源访问 
    res.header("Access-Control-Allow-Headers", "X-Requested-With");
    res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");//允许访问的方式 
    res.header("X-Powered-By",' 3.2.1')
    res.header("Content-Type", "application/json;charset=utf-8");
    next();
});
//后使用api
app.use(api);