Iterate through an array to match result - arrays

Question

I have an array where any of the elements could have a match with a mongodb collection.
var elementsArray = ["item1", "item2", "item3"];
db.getCollection("myCollections").aggregate([
...
{ $group: {...} },
{
$match: {
for(item in elementsArray ){ // this for loop is not appropriate but to give the idea
$or:[
{ "word": item },
{ "preferredWord": item },
{ "synonym": item }
],
}
}
}
])
I know the for loop is inappropriate here but how can iterate through the elementsArray to find a match with any of the keywords (word, preferredWord, or synonym) that can perform the similar operations if the for loop was allowed like this?
Thanks

Answer 1

You can run your array outside of Aggregate, by just creating an array and including it inside of your Aggregate query:
var elementsArray = ["item1", "item2", "item3"];
var orArray = [];
for (item in elementsArray ) {
orArray.push( { "word": elementsArray[item], "preferredWord": elementsArray[item], "synonym": elementsArray[item] } );
}
Then you can use orArray object inside your aggregate:
db.getCollection("myCollections").aggregate([
...
{ $group: {...} },
{
{
$match: {
"$or" : orArray
}
}
]);

Answer 2

You can use the $in aggregation operator to match a field with elements from the array. You can add the other aggregation stages where appropriate (I cannot specify the entire query without the definition of the collection's input document)
Example matches collection:
{ _id: 1, fld1: "blah", word: "item2", synonym: "item3" }
{ _id: 2, fld1: "zzz", word: "item1", synonym: "item2" }
{ _id: 3, fld1: "123", word: "item99", synonym: "item99" }
The Query (from mogo shell):
var arr = [ "item1", "item2" ];
db.matches.aggregate( [
{
$addFields: {
"hasMatches": { $or: [ {$in: [ "$word", arr ]}, {$in: [ "$synonym", arr ]} ] }
}
},
{
$match: { hasMatches: true }
}
] )
The Output:
{ "_id" : 1, "fld1" : "blah", "word" : "item2", "synonym" : "item3", "hasMatches" : true }
{ "_id" : 2, "fld1" : "zzz", "word" : "item1", "synonym" : "item2", "hasMatches" : true }