DynamoDB Document SDK in Javascript
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Alexander Patrikalakis
Alexander Patrikalakis Merge pull request #48 from DoWhileGeek/patch-1
fix a syntax error in README
Latest commit c0124d7 Apr 24, 2017

README.md

DynamoDB Document SDK

NOTE: As of September 10, 2015, this version of the Document SDK will be deprecated in favor of the AWS.DynamoDB.DocumentClient in the official AWS SDK for JavaScript. This repository will continued to be hosted, but not maintained outside of bug reports. In addition, discussion and request for guidance should be directed at the official AWS SDK for JavaScript. Here's how you can get started with the new client!


This SDK abstracts away the typing of attribute values in the low level SDK in order to provide a simpler developing experience. JS datatypes like string or number can be passed directly into DynamoDB requests and the wrapping will be handled for you; similarly for responses, datatypes will be unwrapped.

For those DynamoDB types that do not have direct mappings to JS datatypes, a wrapper Object is provided to handle type ambiguities (i.e. StrSet, NumSet, BinSet).

Lastly, a Condition Object is being introduced to simplify the use of the KeyCondition and Expected portion of the request params. Note: Condition Object serves to simplify previous api (NOT new expressions)

Getting Started

Install

$ npm install dynamodb-doc --save

In order to instantiate the client, you still need the AWS JS SDK to store your region/credentials.

var AWS = require("aws-sdk");
var DOC = require("dynamodb-doc");

AWS.config.update({region: "us-west-1"});

var docClient = new DOC.DynamoDB();

Alternatively if you already have the existing DynamoDB Client, you can pass it in order to instantiate the client.

// assumes AWS.config is set up already
var awsClient = AWS.DynamoDB();
var docClient = new DOC.DynamoDB(awsClient);

After this, you can make requests and receive responses with JS datatypes!

JS datatypes that can be used in place of DynamoDB Datatypes:

Javascript DynamoDB
string S
number N
boolean BOOL
null NULL
array L
object M

For Sets, the client will provide object for you:

docClient.Set(["a", "b", "c"], "S")

Refer to the Basic Usage and Nested DataTypes and More sections down below to see examples of the updated API.

In addition, the SDK also introduces a special kind of Object in order to simplify conditions.

docClient.Condition(key, operator, val1, val2)

Refer to the section down below on Condition Objects to see an example of the usage.

NOTE: To build the node js files for the browser yourself, run

npm install; uglifyjs lib/* | sed 's/\"use strict\";//' > dynamodb-doc.min.js
# sed portion is optional depending on your use case

For each example assume we have these variables available to us.

// Basic Client creation
AWS.config.update({ /* ...your config... */ });
docClient = new DOC.DynamoDB();

// Basic Callback
var pfunc = function(err, data) { 
    if (err) {
        console.log(err, err.stack);
    } else {
        console.log(data);
    }
}

Basic Usage:

// Basic Scalar Datatypes
var params = {};
params.TableName = "Users";
params.Item = {UserId : "John",
               Age    : 21,
               Pic    : docClient.StrToBin("someURI")};

docClient.putItem(params, pfunc);

params = {};
params.TableName = "Users";
params.Key = {UserId : "John"};

docClient.getItem(params, pfunc); 

/* Response
{Item: {UserId : "John",
       Age     : 21,
       Pic     : Bin}} 
*/

NOTE: StrToBin returns either a Buffer for NodeJS or Uint8Array for the browser.

Nested DataTypes and More:

var params = {};
params.TableName = "Shopping Cart";

// Compatible is a Map of Part to List of PartId's
// OnSale is a BOOL type
// Discount is a NULL type
params.Item = {PartId       : "CPU1",
               OnSale       : false,
               Discount     : null,
               Compatible   : {Motherboards : ["MB1", "MB2"],
                               RAM          : ["RAM1"]}};

docClient.putItem(params, pfunc);

params = {};
params.Key = {PartId : "CPU1"};
params.TableName = "Shopping Cart";

docClient.getItem(params, pfunc);

/*Response
{Item: {PartId : "CPU1",
        OnSale : false,
        Discount : null,
        Compatible : {Motherboards : ["MB1", "MB2"],
                      RAM          : ["RAM1"]}}};
*/

Condition Object:

var params = {};
params.TableName = "Houses";

// Note: This is a query on the Key Schema of the table.  
// For queries on secondary indexes, specify params.IndexName = "index-name"

// use an array of Condition Objects for multiple conditions
params.KeyConditions = [docClient.Condition("HouseId", "NOT_NULL"),
                        docClient.Condition("YearBuilt", "GT", 2000)];

// use a Condition Object for just a single condition
params.QueryFilter = docClient.Condition("Price", "BETWEEN", 0, 900000);

docClient.query(params, pfunc);

/*Reponse
{Count: 3,
Items: [ { HouseId   : "123 amzn way",
           YearBuilt : 2001,
           Price     : 450000},
         { HouseId   : "321 dynamo st",
           YearBuilt : 2012,
           Price     : 100000},
         { HouseId   : "213 JS ave",
           YearBuilt : 2014,
           Price     : 1}],
ScannedCount: 3}
*/

Expressions (NEW!!):

var params = {};
params.TableName = "SomeTable";
params.Key = {Some : "Key"};
    
// Use the #(variable) to substitute in place of attribute Names
// Use the :(variable) to subsitute in place of attribute Values
params.UpdateExpression = "set #a = :x + :y";
params.ConditionExpression = "#a < :MAX and Price = :correct";
params.ExpressionAttributeNames = {"#a" : "Description"};
params.ExpressionAttributeValues = {":x" : 20,
                                    ":y" : 45,
                                    ":MAX" : 100,
                                    ":correct" : "is right!!"};

docClient.updateItem(params, pfunc);