Add support for $expr

[felipecarrillo100]

mingo.zip

I have modified the mingo.js from the distribution directory to support the $expr operator.

This operator is introduced in Mongo 3.6 and it allows to use expression (such as arithmetic operations) in a query. It also allows comparing 2 fields against eachothr.

Example:
{"$expr":{"$gt":[{"$multiply":["$value1", 2]}, "$value2"]}}

The "$expr" offers advantages over "$where" and it seems easy to implement from the building blocs already available in your implementation. I just had to modify a few lines (Do find "$expr").

I'm not sure how to build the project but it would be great if you can add this feature. Use the code in my attachment as reference.

Thanks in advance

[kofrasa]

Thanks for the contribution @felipecarrillo100 I will take a look at this soon.

[kofrasa]

Added in commit 4a75f03

This will be going in the 2.2.1 release. You can play around with the changes in branch:development