check substring in mongo - node.js

Question

I have filter with mongo aggregation:
query['$or'] =
{
firstName: {
$search: filter.keyword,
},
},
{
lastName: {
$regex: filter.keyword, $options: 'xi',
},
},
And later I attach the query to the aggregation.
Have user: firstName: 'john'. lastName: 'snow'.
If filter.keyword = 'jo', 'john', 'john ', all work, return 1 result, but if filter.keyword = 'john s', return 0.
I understand that I need to check not with regex but on the occurrence of the field value in the resulting string, then all subsequent characters will be ignored and the result will be returned to me. I can’t split, and check for an entry in the array, it will give an error for complex names.
This is probably a very stupid question, but I can’t verify the occurrence of the name John in the string 'John S'.
Later query will be attached to aggregation in $match.
Thanks for your answers!!!

Answer 1

You can continue to use regex and break word :
filter.keyword.split(" ").join("|")
This will search for firstname matching "john" or "s" :
$regex: "john|s"
Otherwise you can directly use $text : https://docs.mongodb.com/manual/reference/operator/query/text/
But it will apply a $or on each word, as the solution i propose
And finally you can use $indexOfBytes (substring search):
db.a.insert({name: "john", firstname: "snow"})
db.a.aggregate([{$project: {byteLocation:{$indexOfBytes:["john s", "$name"]}}}])
// { "_id" : ObjectId("5cadb07ddf1f1fe1647e252f"), byteLocation: 0}
db.a.aggregate([{$project: {byteLocation:{$indexOfBytes:["f john s", "$name"]}}}])
// { "_id" : ObjectId("5cadb07ddf1f1fe1647e252f"), byteLocation: 2}