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dynamodb-data-types

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Readme

DynamoDb-Data-Types

This utility helps represent AWS DynamoDb data types. It maps (marshalls) JavaScript data into the format required by DynamoDb.

For example, following is some JavaScript data:

var data = { 
  name: 'Java Script',
  age: 18,
  fav: {
    food: ['Rice', 'Noodles'],
    colors: ['Orange', 'Blue']
  },
  engines: [ 'Rhino', 'v8', 'SpiderMonkey', 'Carakan', 'JavaScriptCore' ]
}

To put the above JavaScript data into DynamoDB, the AWS SDK requires it to be mapped to the following format:

{
  "name": { "S": "Java Script" },
  "age": { "N": "18" },
  "fav": { 
    "M": {
      "food": { "SS": [ "Rice", "Noodles" ] },
      "colors": { "SS": ["Orange", "Blue" ] }
    }
  },
  "engines": { "SS": ["Rhino", "v8", "SpiderMonkey", "Carakan", "JavaScriptCore" ] }
}

This library maps it for you.

Use wrap to map (marshall) data into the format required by DynamoDB's AttributeValue:

var attr = require('dynamodb-data-types').AttributeValue;
attr.wrap(data);
// {
//   "name": { "S": "Java Script" },
//   "age": { "N": "18" },
//   "fav": { 
//     "M": {
//       "food": { "SS": [ "Rice", "Noodles" ] },
//       "colors": { "SS": ["Orange", "Blue" ] }
//     }
//   },
//   "engines": { "SS": ["Rhino", "v8", "SpiderMonkey", "Carakan", "JavaScriptCore" ] }
// }

Use unwrap to unmarshall data received from DynamoDB.

Use with Node.js

Use with AWS SDK for Node.js

npm install dynamodb-data-types

Use in the browser

Use with AWS SDK for JS in the Browser

Download the browser version from dist . See examples/browser and this note

Quick Examples

var attr = require('dynamodb-data-types').AttributeValue;

var infoAttrValue = attr.wrap({ name: "Foo", age: 50 });
console.log(JSON.stringify(infoAttrValue));
// {"name":{"S":"Foo"},"age":{"N":"50"}}

var experience = {
  count: {"N": "4" },
  languages: { "SS": ["Java Script", "Ruby", "GLSL", "C" ] }
}
console.log(JSON.stringify(attr.unwrap(experience)));
// {"count":4,"languages":["Java Script","Ruby","GLSL","C"]}

Notes for use in the browser

The browser version of this library (created using browserify) has not been tested. It is written using basic JavaScript and should work in most browsers. Pull requests to add tests for the browser are welcome (maybe using phantom.js?).

The browser version is available from version 2.1.2 onwards.

File size of the browser version

The file size of the browser version (dist/dynamodb-data-types.js ) is much larger than what is should be. It is generated using Browserify. Since the node version of the library uses Buffer for dealing with binary types, browserify inlcudes Buffer related, which should not be needed on the browser side. If Buffer code were to be excluded for the browser version, file size would reduce by a factor of 5.

Pull requests related to this are welcome.

Examples

Features

Refer to docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Types.html

DynamoDb-Data-Types supports:

AttributeValue
AttributeValueUpdate

Supported AttributeValue types

Refer to docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_AttributeValue.html

DynamoDb-Data-Types supports:

B
BOOL
BS
L
M
N
NS
NULL
S
SS

wrapping data

Its trivial to detect N, NS, S, SS, NULL and BOOL. The other types M, L, B, BS are not difficult but need some explaining.

For any a given value val, wrap() detects the AWS Data types as follows:

BOOL, NULL, N, S

How wrap() detects them (psuedo-code):

IF val is typeof boolean
    THEN detect as type BOOL
ELSE IF val is null
    THEN detect as type NULL
ELSE IF val is typeof number or if val instanceof Number
    THEN detect as type N
ELSE IF val is typeof string or if val is instanceof String
    THEN detect as type S

B

How wrap() detects type B (psuedo-code):

IF val is instanceof Buffer
    THEN detect as type B

There maybe other types which should get detected as B. Please let me know if you have suggestions.

M

How wrap() detects type M (psuedo-code):

IF (val is none of: BOOL, NULL, N, S, B)
    AND (typeof val === 'object')
        THEN detect as type M
ELSE
    wrap() ignores val

NS, SS, BS, L

When wrap() sees an Array, here's what it does (psuedo-code):

IF val is an Array
    IF (every element in Array is type N)
        THEN detect as type NS
    ELSE IF (every element in Array is type S)
        THEN detect as type SS
    ELSE IF (every element in Array is type B)
        THEN detect as type BS
    ELSE 
        detect as type L

What's new in version 2.1.0

Consider the following:

var data = {
  alphabets: ['c', 'a', 'b', 'c']
};

wrap(data) detects alphabets as SS. Being a set SS has two properties unlike those of arrays :

The order of elements is not preserved.
Duplicate elements are not allowed.

Starting with version 2.1.0, you can do:

wrap(data, {types: {alphabets: 'L'} } to explicitly tell wrap to treat it L instead of the auto-detected SS. Similarly for put() and add()
Alternatively, call preserveArrays() to consider all arrays as type L. This has a global effect.

Read the documentation and examples for more.

What's new in version 2.0.0

DynamoDb-Data-Types version 2.0.0 introduces support for AttributeValue types BOOL, NULL, M, L.

Use of `M` for nested data

DynamoDb-Data-Types uses M to nest objects. Consider the following data:

var data = {
  polygon: {
    quadrilateral: {
        sides: 4
    }
  }
}

wrap() maps the above data as:

{
  "polygon": {
    "M": {
      "quadrilateral": {
        "M": {
          "sides": {
            "N": "4"
          }
        }
      }
    }
  }
}

Use of `L` for arrays

DynamoDb-Data-Types uses L to represent mixed arrays. Consider the following data:

{
  strs: ['abc', 'def'],
  nums: [123, 456],
  mix: [1, 'abc', true, false, null, [1,2,3]]
}

wrap() maps the above data as:

{
  strs: { 
    SS: ["abc","def"] 
  },
  nums: { 
    NS: ["123","456"] 
  },
  mix: {
    "L": [
      { N: "1" },
      { S: "abc" },
      { BOOL: true },
      { BOOL: false },
      { NULL: true },
      { NS: ["1","2","3"] }
    ]
  }
}

Documentation

Global settings

preserveArrays()

If preserveArrays() is called, all arrays found in the object being wrapped are given type L. In other words, arrays will no longer get detected as NS, SS or BS but specified as L.

This is useful to preserve duplicates and the order of elements in arrays.

var ddt = require('dynamodb-data-types');
ddt.preserveArrays();

This function is designed to be called once - It has a global effect.

If this is not needed on a global level, a similar effect can be achieved using options parameter passed to wrap(), wrap1() and put() and add().

Similarly, the global behaviour of preserveArrays() may be overridden using the options object passed to wrap(), wrap1() and put() and add().

AttributeValue

AWS API Reference - AttributeValue

wrap
unwrap
wrap1
unwrap1

AttributeValueUpdate

AWS API Reference - AttributeValueUpdate

put
add
delete

AttributeValue

wrap(item[, options])

Wrap (marshall) JavaScript data into DynamoDB's AttributeValue data type.

Arguments

@param {Object} item The object to wrap.
@param {Object} options
@return {Object} A DynamoDb AttributeValue.

Options

types: An object containing attribute names and explicit type for that attribute. Currently explicit type can only be specified if the detected type is an array. Possible values are 'NS', 'SS', 'BS', 'L'

Example of an options object:

// Any property named 'randomList' found in the object (at any depth) is
// specified as 'NS'. This explicit type can be assigned only if `randomList` is
// detected as an array.

// Similarly if 'orderedList' is an array, it gets specified as type 'L'

{
  types: {
     randomList: 'NS', 
     orderedList: 'L'
  }
}

Example

var attr = require('dynamodb-data-types').AttributeValue;
attr.wrap({name: "Foo", age: 50});
// {"name":{"S":"Foo"},"age":{"N":"50"}}

attr.wrap({alphabets: ["a", "b", "c"]});
// {"alphabets":{"SS": ["a","b","c"]}}

attr.wrap({alphabets: ["a", "b", "c"]}, {types: {alphabets:"L"}});
// {"alphabets":{"L": [{"S":"a"},{"S":"b"},{"S": "c"}]}}

unwrap(attributeValue)

Unwrap (unmarshall) DynamoDB AttributeValue to appropriate JavaScript types.

Arguments

@param {Object} attributeValue The DynamoDb AttributeValue to unwrap.
@return {Object} Unwrapped object with properties.

Example

var attr = require('dynamodb-data-types').AttributeValue;
attr.unwrap({"name":{"S":"Foo"},"age":{"N":"50"}});
// {name: "Foo", age: 50}

wrap1(value [, options])

Wrap a single value into DynamoDB's AttributeValue.

Arguments

@param {String|Number|Array}
@param {Object} options Same as options for wrap().
@return {Object} DynamoDB AttributeValue.

Example

var attr = require('dynamodb-data-types').AttributeValue;
attr.wrap1(50);    // {"N":"50"}
attr.wrap1("50");  // {"S":"50"}

unwrap1(attributeValue)

Unwrap a single DynamoDB's AttributeValue to a value of the appropriate JavaScript type.

Arguments

@param {Object} attributeValue The DynamoDB AttributeValue. @return {String|Number|Array} The JavaScript value.

Example

var attr = require('dynamodb-data-types').AttributeValue;
attr.unwrap1({"N":"50"});  // 50
attr.unwrap1({"S":"50"});  // "50"

AttributeValueUpdate

add(attrs [, options])

Append attributes to be updated with action "ADD". This function can be chained with further calls to add, put or delete.

Arguments

@param {Object} attrs Object with attributes to be updated.
@param {Object} options Same as options for wrap().
@return {Updates} Object with all update attributes in the chain.

Example - put, add, delete.

See note: duplicate attribute names

put(attrs [, options])

Append attributes to be updated with action "PUT". This function can be chained with further calls to add, put or delete.

Arguments

@param {Object} attrs Object with attributes to be updated.
@param {Object} options Same as options for wrap().
@return {Updates} Object with all update attributes in the chain.

Example - put, add, delete.

See note: duplicate attribute names

delete(attrs)

Append attributes to be updated with action "DELETE". This function can be chained with further calls to add, put or delete.

Arguments

@param {Object|String|Array} attrs If this argument is an an Object,the Object's property values must be an array, containing elements to be removed, as required by DynamoDb SDK. If this argument is a String, it should contain comma seperated names of properties to be deleted. If its an Array, each array element should be a property name to be deleted.
@return {Updates} Object with all update attributes in the chain.

See note: duplicate attribute names

Example: `put`, `add`, `delete`

var attrUpdate = require('dynamodb-data-types').AttributeValueUpdate;

var dataUpdate = attrUpdate
    .put({name: "foo"})
    .add({age: 1})
    .delete("height, nickname")
    .add({favColors: ["red"]})
    .delete({favNumbers: [3]});

console.log(JSON.stringify(dataUpdate));
// {
//   "name": { "Action": "PUT", "Value": { "S": "foo" } },
//   "age": { "Action": "ADD", "Value": { "N": "1" } },
//   "height": { "Action": "DELETE" },
//   "nickname": { "Action": "DELETE" },
//   "favColors": { "Action": "ADD", "Value": { "SS": ["red" ] } },
//   "favNumbers": { "Action": "DELETE", "Value": { "NS": ["3"] } }
// }

Note: Duplicate attribute names in `AttributeValueUpdate`

Each attribute name can appear only once in the AttributeUpdates object of the itemUpdate call. This is a feature of the AWS API. However its easy to overlook this when chaining add, put and delete updates.

For example, following is an attribute colors of type SS (String set)

var item = {
    id: ...,
    colors: ["red", "blue"]
}

Suppose, we want to delete "red" and add "orange".

To add "orange", the AttributeUpdates object is created as: attrUpdate.add({colors: ["orange"]}). Similarly, to delete "red" the AttributeUpdates object is created as attrUpdate.delete({colors: ["red"]})

However, both actions cannot be represented in the same AttributeUpdates object.

// Will not work as expected
attrUpdate.add({colors: ["orange"]}).delete({colors: ["red"]});

The action to delete "red" overwrites the action to add "orange". This is simply because colors is a property of the AttrubuteUpdates object.

The following code demonstrates the above note:

JSON.stringify(attrUpdate.add({colors: ["orange"]}));
//{"colors":{"Action":"ADD","Value":{"SS":["orange"]}}}

JSON.stringify(attrUpdate.delete({colors: ["red"]}));
//{"colors":{"Action":"DELETE","Value":{"SS":["red"]}}}

// The below does not work as expected
JSON.stringify(attrUpdate.add({colors: ["orange"]}).delete({colors: ["red"]}));
//{"colors":{"Action":"DELETE","Value":{"SS":["red"]}}}

Older versions of DynamoDb-Data-Types

Read this only if you need DynamoDb-Data-Types version 1.0.0 or below.

If you are already using version 1.0.0 or 0.2.7 you may continue to do so.

If you are using DynamoDb-Data-Types version 1.0.0 or 0.2.7, wrapping / unwrapping B and BS will not work when used with AWS SDK 1.x.x but should automagically work with AWS SDK 2.x.x. although it has not been tested. This is related to automatic conversion of base64 done by AWS SDK version 2.x. See AWS Upgrading Notes (1.x to 2.0).

Change log

Version 2.1.3

Add tests to imporve coverage.

Apart from added tests,2.1.3 is idential to 2.1.2

Version 2.1.2

This version is identical to 2.1.1 with no changes to code. It only includes a JS build for the browser plus a few more tests.

Use browserify to create a dist for use in the browser.
Updated tests, use travis-ci, coverage, istanbul, .jshintrc.

Version 2.1.1

2015-12-18

Replace functions deprecated by Node.

Version 2.1.0

2015-08-17

Call preserveArrays() to use type L for array types; this preserves order of array elements and allows duplicate array elements both of which are not possible using sets SS, NS or BS
If not required on a global scale (calling preserveArrays), explicity set array types by passing opts to wrap(), add(), put()

Version 2.0.1

2015-02-15

Fixed README
Committed modified package.json (just realised it wasn't committed)

Version 2.0.0

2015-02-15

Implemnted M
Implemented L
Added example to put and get binary data (examples/02-binary-image.js)

Version 1.0.0

2015-02-11

Note: There are no source code changes in version 1.0.0. Functionally, 1.0.0 is identical to 0.2.7.

Bumped from version 0.2.7 to version 1.0.0.
Update documentation especially with regard to B and BS data types.
Added development deps into pacakge.json instead of tests/package.json (It should have been this way to begin with)

version 0.2.7

2014-01-29

version 0.2.6

2013-11-15

version 0.2.5

2013-11-11

Note: Change log dates are yyyy-mm-dd.