Cannot proxy after parsing body

I cannot re-send a proxied request’s body after I have parsed it.

Using this recipe, this comment and this comment I have written the following example:

import express from 'express';
import proxy from 'http-proxy-middleware';
import bodyParser from 'body-parser'

const app = express();
app.use(bodyParser.json());
app.post('*', proxy({
    target: 'http://target.here.com',
    secure: false,
    onProxyReq: (proxyReq, req) => {
        if (req.body) {
            const bodyData = JSON.stringify(req.body);
            proxyReq.setHeader('Content-Type','application/json');
            proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
            proxyReq.write(bodyData);
        }
    }
}));
app.listen(2001, () => console.log('Listening'));

I get an error when trying to set the first header on the proxyReq saying: Cannot set headers after they are sent to the client.

If that is the case how does the recipe work?

[SBRK]

+1 got the same issue. Moving the middlewares before body.json works

[windix]

If need to parse the body before proxy, I have followed suggestion from this issue: https://github.com/chimurai/http-proxy-middleware/issues/177#issuecomment-420423934