Randomizing unique data with MongoDB and placing values for emailid with wordJohn in the beginning

To randomize unique data, use Math.random() in MongoDB. Let us create a collection with documents −

> db.demo561.insertOne({EmailId:null});{
   "acknowledged" : true, "insertedId" : ObjectId("5e8f490454b4472ed3e8e86c")
}
> db.demo561.insertOne({EmailId:null});{
   "acknowledged" : true, "insertedId" : ObjectId("5e8f490654b4472ed3e8e86d")
}
> db.demo561.insertOne({EmailId:null});{
   "acknowledged" : true, "insertedId" : ObjectId("5e8f490a54b4472ed3e8e86e")
}

Display all documents from a collection with the help of find() method −

> db.demo561.find();

This will produce the following output −

{ "_id" : ObjectId("5e8f490454b4472ed3e8e86c"), "EmailId" : null }
{ "_id" : ObjectId("5e8f490654b4472ed3e8e86d"), "EmailId" : null }
{ "_id" : ObjectId("5e8f490a54b4472ed3e8e86e"), "EmailId" : null }

Following is the query for randomizing unique data with MongoDB −

> db.demo561.find().forEach(function(doc){
...    db.demo561.update({_id : doc._id}, {$set:{
...       EmailId:'John'+Math.random()*100000000000000000+'@'+Math.random()*100000000000000000+'.com'
...    }})
... })

Display all documents from a collection with the help of find() method −

> db.demo561.find();

This will produce the following output −

{ "_id" : ObjectId("5e8f490454b4472ed3e8e86c"), "EmailId" : "John23607829153155868@62688631475897960.com" }
{ "_id" : ObjectId("5e8f490654b4472ed3e8e86d"), "EmailId" : "John63351292234094710@79460595429439740.com" }
{ "_id" : ObjectId("5e8f490a54b4472ed3e8e86e"), "EmailId" : "John71315584787457890@99884571221675000.com" }