Mongo Update Query on Array Index value matching - mongodb

Question

student collection look like below.
[{
"_id" : NumberLong(1),
"studentId" : "70133",
"subjects" : [
"Mathematics",
"Biology and Zoology"
]
},
{
"_id" : NumberLong(2),
"studentId" : "70134",
"subjects" : [
"Mathematics",
"English"
]
},
{
"_id" : NumberLong(3),
"studentId" : "70135",
"subjects" : [
"English",
"Mathematics",
"Chemistry"
]
}]);
I want to write a query which will update the student collection subject array values like this:
If subject matches English have to be updated to ENG
If subject matches Biology and Zoology have to be updated to BAZ
If subject matches Mathematics have to be updated to MAT
If subject matches Chemistry have to be updated to CHM
After update documents should look like below. How Can I achieve this.
[{
"_id" : NumberLong(1),
"studentId" : "70133",
"subjects" : [
"MAT",
"BAZ"
]
},
{
"_id" : NumberLong(2),
"studentId" : "70134",
"subjects" : [
"MAT",
"ENG"
]
},
{
"_id" : NumberLong(3),
"studentId" : "70135",
"subjects" : [
"ENG",
"MAT",
"CHM"
]
}]);

Answer 1

This has to be done with multiple updates like:
db.collection.update(
{ "subjects" : { $in : [ "Mathematics" ] } },
{ $set: { "subjects.$" : "MAT" } },
{ multi: true }
)
See this page for more information regarding updating multiple document
if multi is set to true, the db.collection.update() method updates all documents that meet the criteria. The multi update operation may interleave with other read/write operations.
https://docs.mongodb.com/master/reference/method/db.collection.update/index.html#multi-parameter