AWS.DynamoDB.DocumentClient is not providing data on put - node.js

Question

I am using the AWS.DynamoDB.DocumentClient, with Dynamodb local (port 8080). When I perform a put, the data variable in the callback is an empty object. Have I missed something?
import * as AWS from "aws-sdk";
AWS.config.update({
region: "us-west-2",
endpoint: "http://localhost:8080"
});
const docClient: any = new AWS.DynamoDB.DocumentClient();
const item = {
someField: "456",
other: "123"
};
const params = {
TableName: "TableName",
Item: item
};
docClient.put(params, function(err, data) {
if (err) console.log(err);
else console.log(data); // this produces: {}
});
There is no error, and the item is being inserted\updated - however the data variable is an empty object. Shouldn't this contain values?
Thanks

Answer 1

You aren't asking for any values to come back, so why do you expect there to be any values coming back? You'll need to set the appropriate parameters ReturnConsumedCapacity and/or ReturnItemCollectionMetrics and/or ReturnValues if you are wanting any of that to come back in the response.

Answer 2

As you can't set a value for "ReturnValues" that actually returns anything useful, I worked around it by simple passing back the original item data that was passed in.
import * as AWS from "aws-sdk";
AWS.config.update({
region: "us-west-2",
endpoint: "http://localhost:8080"
});
const docClient: any = new AWS.DynamoDB.DocumentClient();
const item = {
someField: "456",
other: "123"
};
const params = {
TableName: "TableName",
Item: item
};
// Have a clear reference to this scope
var self = this;
docClient.put(params, function(err, data) {
if (err) console.log(err);
else console.log(self.params.Item); // this should return the data you passed in!
});
I set "self" as "this" to make it clear where I'm reading the data from. Hope that helps someone!

Answer 3

To clarify accepted answer a bit.
Set the return value as:
var params = {
Item: data,
TableName: 'myTable',
ReturnValues: 'ALL_OLD'
}
The docs specify:
NONE - If ReturnValues is not specified, or if its value is NONE, then nothing is returned. (This setting is the default for ReturnValues.)
ALL_OLD - If PutItem overwrote an attribute name-value pair, then the content of the old item is returned.
Note: The ReturnValues parameter is used by several DynamoDB operations; however, PutItem does not recognize any values other than NONE or ALL_OLD.
This effectively means as the answer by Walter White describes that unless there is an update to an existing item that nothing will be returned.