Mongodb $where query always true with nodejs

Question

When I query my database with a function passed in the \"$where\" clause in nodejs, it always return me all documents in the db.

For example, if I do

Answer 1

You can use a wrapper to pass basic JSON objects, ie. (pardon coffee-script):

# That's the main wrapper.
wrap = (f, args...) ->
  "function() { return (#{f}).apply(this, #{JSON.stringify(args)}) }"

# Example 1
where1 = (flag) ->
  @myattr == 'foo' or flag

# Example 2 with different arguments
where2 = (foo, options = {}) ->
  if foo == options.bar or @_id % 2 == 0
    true
  else
    false

db.collection('coll1').count $where: wrap(where1, true), (err, count) ->
  console.log err, count

db.collection('coll1').count $where: wrap(where2, true, bar: true), (err, count) ->
  console.log err, count

Your functions are going to be passed as something like:

function () {
    return (function (flag) {
        return this.myattr === 'foo' || flag;
    }).apply(this, [true])
}

...and example 2:

function () {
    return (
        function (foo, options) {
            if (options == null) {
                options = {};
            }
            if (foo === options.bar || this._id % 2 === 0) {
                return true;
            } else {
                return false;
            }
        }
    ).apply(this, [ true, { "bar": true } ])
}