I recently ran into a problem while developing some of our advanced search capabilities on Endorse.me: I wanted to find all the documents in our MongoDB database that had at least one of a number of elements as a property. This is fairly easy to do using MongoDB’s ’$in’ operator when the property is a primitive, like a string:
https://gist.github.com/4599048
But what if one of our toys has multiple colors, listed in an array? I searched around for a some sort of $any operator before looking again at the MongoDB documentation for $in. Turns out, if the field has an array, it behaves exactly how I was hoping it would!