dynamoDb-marshaler

Translates sane javascript objects (and JSON) into DynamoDb format and vice versa.

Caveat Does not yet work with Binary types (B and BS). I have personally never come across a case where I'm using binary types in json. If you need binary support, please let me know how it might be done, or contribute.

Why?

Translation of DynamoDb AttributeValue objects is cumbersome and makes working with the aws-sdk-js more difficult than it needs to be. This library abstracts away the verbose tiresome mappings and lets you work with standard javascript (JSON) data like you're used to.

Install

npm install dynamodb-marshaler

Basic Marshaling

var AWS = require('aws-sdk');
var marshalItem = require('dynamodb-marshaler').marshalItem;
    
AWS.config.region = 'us-west-2';
var dynamoDb = new AWS.DynamoDB();

dynamoDb.putItem({
  TableName: 'users',
  Item: marshalItem({username: 'nackjicholson'})  // {username: {S: 'nackjicholson'}}
});

Basic Unmarshaling

var AWS = require('aws-sdk');
var unmarshalItem = require('dynamodb-marshaler').unmarshalItem;
    
AWS.config.region = 'us-west-2';
var dynamoDb = new AWS.DynamoDB();

var data = dynamoDb.scan({
  TableName: 'users'
}, function(err, data) {
  // data.Items = [{username: {S: 'nackjicholson'}]
  var items = data.Items.map(unmarshalItem);
  console.log(items); // [{username: 'nackjicholson'}]
});

JSON

You can marshal directly from a JSON string. Or unmarshal a DynamoDb api response into a JSON string. Use marshalJson and unmarshalJson.

Examples

More extensive examples can be found in the examples directory.

Understanding the rules

Empty strings

DynamoDB does not allow saving of an empty string "". The marshaler treats this as an error.

Sets vs Lists

Javascript has one list type -- arrays, but DynamoDB has sets and lists. How does the marshaler distinguish between the two?

Here's a table:

	input	marshaled value
Strings/No duplicates	["foo", "bar"]	{"SS": ["foo", "bar"]}
Numbers/No duplicates	[42, 43]	{"NS": ["42", "43"]}
Empty	[]	{"L": []}
Mixed	[42, "foo", null]	{"L": [{"N": "42"}, {"S": "foo"}, {"NULL": true}]}
Duplicates	["foo", "bar", "foo"]	{"L": [{"S": "foo"}, {"S": "bar"}, {"S": "foo"}]}

Contributions

Please contribute. But make sure test coverage is 100% and that the code complies with the Cascade Energy Style Guide for NodeJs

rockykitamura/dynamoDb-marshaler