Middleware to turn off caching
==============================
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It's possible that you've got bugs in an old HTML or JavaScript file, and with a cache, some users will be stuck with those old versions. This will (try to) abolish all client-side caching.

```javascript
var nocache = require('nocache')
app.use(nocache())
```

This sets four headers, disabling a lot of browser caching:

- `Cache-Control: no-store, no-cache, must-revalidate, proxy-revalidate`
- `Pragma: no-cache`
- `Expires: 0`
- `Surrogate-Control: no-store`

If you want to crush the `ETag` header as well, you can:

```javascript
app.use(nocache({ noEtag: true }))
```

Caching has some real benefits, and you lose many of them here. Browsers won't cache resources with this enabled, although *some* performance is retained if you keep ETag support. It's also possible that you'll introduce *new* bugs and you'll wish people had old resources cached, but that's less likely.