Node 心中有坑，处处是坑

记录一个 Node 的坑

新手接触 Node 不到一个月，遇到了很多坑

后端代码是这样写的：

app.all('*', function(req, res, next) { res.header("Access-Control-Allow-Origin", "*"); res.header("Access-Control-Allow-Headers", "Cntent-Type,Content-Length, Authorization, Accept,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="); next(); }); 

然而前端每次发送 AJAX 跨域请求时都收不到结果，错误信息为网关超时

 XMLHttpRequest cannot load http://111.111.111.111:8089/login_service. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://111.111.111.111' is therefore not allowed access. The response had HTTP status code 504. 

后来发现前端使用 CORS 请求时content-type取值为application/json; charset=，也就是说发送跨域请求时会发送 OPTIONS 预检请求，而我没有对设置 OPTIONS 路由，因此成功入坑。后来把后端代码改为了

app.all('*',function (req, res, next) { res.header('Access-Control-Allow-Origin', '*'); res.header('Access-Control-Allow-Headers', 'Content-Type, Content-Length, Authorization, Accept, X-Requested-With , yourHeaderFeild'); res.header('Access-Control-Allow-Methods', 'PUT, POST, GET, DELETE, OPTIONS'); if (req.method == 'OPTIONS') { console.log('you can do that!!'); res.send(200); // 让 options 请求快速返回 } else { next(); } }); 

写在最后

从坑中出来了，颇有感慨。顺便记录了一下对 CORS 跨域的探索，可能是知识盲点太多所以入坑太多，Node 的路上你遇到了哪些坑？求各位告知。