no cache in a nodejs server

Problem

I have read that to avoid cache in nodejs it is necessary to use:

"res.header('Cache-Control', 'no-cache, private, no-store, must-revalidate, max-stale=0, post-check=0, pre-check=0');"

But I don't know how to use it because I get errors when I put that line in my code.

My function (where I think I have to program no cache) is:

function getFile(localPath, mimeType, res) {
        fs.readFile(localPath, function(err, contents) {
                if (!err) {
                    res.writeHead(200, {
                    "Content-Type": mimeType,
                    "Content-Length": contents.length,
                'Accept-Ranges': 'bytes',
                    });
                //res.header('Cache-Control', 'no-cache');
                    res.end(contents);
                } else {
                    res.writeHead(500);
                    res.end();
                }
        });

}

Does anyone know how to put no cache in my code? thanks

Problem courtesy of: user2986808

Solution

You've already written your headers. I don't think you can add more after you've done that, so just put your headers in your first object.

res.writeHead(200, {
  'Content-Type': mimeType,
  'Content-Length': contents.length,
  'Accept-Ranges': 'bytes',
  'Cache-Control': 'no-cache'
});
Solution courtesy of: Brad

Discussion

Pylinux's answer worked for me, but upon further inspection, I found the helmet module for express that handles some other security features for you.

http://webapplog.com/express-js-security-tips/

To use, install and require helmet in express.js, then call app.use(helmet.noCache());

Discussion courtesy of: Brian Wells

Make use of a middleware to add no-cache headers. Use this middleware where-ever you intend to turn caching off.

function nocache(req, res, next) {
  res.header('Cache-Control', 'private, no-cache, no-store, must-revalidate');
  res.header('Expires', '-1');
  res.header('Pragma', 'no-cache');
  next();
}

Use the middleware in your routes definition:

app.get('/getfile', nocache, sendContent);

function sendContent(req, res) {
  var localPath = 'some-file';
  var mimeType = '';
  fs.readFile(localPath, 'utf8', function (err, contents) {
    if (!err && contents) {
      res.header('Content-Type', mimeType);
      res.header('Content-Length', contents.length);
      res.end(contents);
    } else {
      res.writeHead(500);
      res.end();
    }
  });
}

Let me know if this works for you.

Discussion courtesy of: vmx

After spelunking through source code for the express and fresh modules, this works from the server side (before res.end is called):

req.headers['if-modified-since'] = undefined;
req.headers['if-none-match'] = undefined;

Nasty, but it works.

Discussion courtesy of: Dale Anderson

Set these headers on your response:

'Cache-Control': 'private, no-cache, no-store, must-revalidate'
'Expires': '-1'
'Pragma': 'no-cache'

If you use express you can add this middleware to have no cache on all requests:

// var app = express()
app.use(function (req, res, next) {
    res.header('Cache-Control', 'private, no-cache, no-store, must-revalidate');
    res.header('Expires', '-1');
    res.header('Pragma', 'no-cache');
    next()
});
Discussion courtesy of: Pylinux

This recipe can be found in it's original form on Stack Over Flow.