I'm working on handling file uploads using express.js and node, and have the basic functionality working. What I need is to implement some security measures -- namely, to limit uploads to certain formats (PNG, JPEG). Is there an easy way to only allow certain formats? Would it go in the body-parser? 

```
app.use(express.bodyParser({
    uploadDir: __dirname + '/public/uploads',
    keepExtensions: true   }));

app.use(express.limit('4mb'));

```

Are there any other security measures that I should take into account? Is it generally a good idea to wipe EXIF data from the image?

Thanks,

Ben