MongoDB Aggregate Match - check if value contains any of the given strings

Question

I have the following types of documents in my mongodb. How can i use a match function to check if the key2 value contains 'Mermaid / Fairy' or 'Superhero'?

  {
    _id: 123,
    key2: [ 'Mermaid / Fairy', 'Superhero' ]
  } 
  {
    _id: 456,
    key2: [ 'Slug']
  } 

This is how i am doing matches for individual words, however i would like to pass in a couple, and if it matches any of them, then it gets returned

    {
      $match: { key2: /.*Superhero.*/ },
    },

Answer 1

Here are a couple of ways ...

to check if the key2 value contains 'Mermaid / Fairy' or 'Superhero'

... by checking if the "$size" of the "$setIntersection" of "$key2" and ["Mermaid / Fairy", "Superhero"]

db.collection.aggregate([
  {
    "$match": {
      "$expr": {
        "$gt": [
          {
            "$size": {
              "$setIntersection": [
                "$key2",
                ["Mermaid / Fairy", "Superhero"]
              ]
            }
          },
          0
        ]
      }
    }
  }
])

Try it on mongoplayground.net.

Another way is to use "$reduce" by checking each "$key2" value to see if it is "$in" ["Mermaid / Fairy", "Superhero"].

db.collection.aggregate([
  {
    "$match": {
      "$expr": {
        "$reduce": {
          "input": "$key2",
          "initialValue": false,
          "in": {
            "$or": [
              "$$value",
              {
                "$in": [
                  "$$this",
                  ["Mermaid / Fairy", "Superhero"]
                ]
              }
            ]
          }
        }
      }
    }
  }
])

Try it on mongoplayground.net.