AWS.DynamoDB.DocumentClient does not provide a way to add number to Number Set.
Need to use lower api Class: AWS.DynamoDB — AWS SDK for JavaScript.
I've tried few times and figured out the sytax of ADD operaion which is not desctibed in UpdateItem reference. Just put .ADD, column name and value
See Modifying Items and Attributes with Update Expressions - Amazon DynamoDB for ADD syntax.
Following code appends given numbers without making dupes.
dynamodb.updateItem({
"TableName" : "mytable",
"Key" : {
"Id": {"S": uuid},
},
"UpdateExpression" : "ADD setname :valuesToAdd",
"ExpressionAttributeValues" : {
": valuesToAdd" : { "NS": ["440"] }
},
ReturnValues:"UPDATED_NEW"
});