Getting express server to accept CORS request

I use cors and implement it so, it's very simple

var cors=require('cors');

app.use(cors({origin:true,credentials: true}));

I personally prefer the cors module. The code is really simple:

var whitelist = [    'http://0.0.0.0:3000',];var corsOptions = {    origin: function(origin, callback){        var originIsWhitelisted = whitelist.indexOf(origin) !== -1;        callback(null, originIsWhitelisted);    },    credentials: true};app.use(cors(corsOptions));

You also need to allow OPTIONS method in the header.

I have this middleware for cors:

module.exports = function (req, res, next) {    // CORS headers    res.header("Access-Control-Allow-Origin", "YOUR_URL"); // restrict it to the required domain    res.header("Access-Control-Allow-Methods", "GET,PUT,POST,DELETE,OPTIONS");    // Set custom headers for CORS    res.header("Access-Control-Allow-Headers", "Content-type,Accept,X-Custom-Header");    if (req.method === "OPTIONS") {        return res.status(200).end();    }    return next();};

PS. The error you get is due to the fact of how cross-origin request works. To make a long story short, the browser might first send a pre-flight request with method OPTIONS to get allowed origins, headers and methods. So for this request you should return nothing but the Access-Control-* headers. If the pre-flight went fine, the browser will continue with the original request.

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