mongo-sanitize

For the passionately lazy, a standalone module that sanitizes inputs against query selector injection attacks:

var sanitize = require('mongo-sanitize');

// The sanitize function will strip out any keys that start with '$' in the input,
// so you can pass it to MongoDB without worrying about malicious users overwriting
// query selectors.
var clean = sanitize(req.params.username);

Users.findOne({ name: clean }, function(err, doc) {
  // ...
});

If sanitize() is passed an object, it will mutate the original object.