#object-mapper#

##About##

This module provides a way to copy properties from one object to another based on a separate object which defines how the properties should be mapped.

##Installation##

$ npm install --save object-mapper

##Usage##

The mapping object is a simple object, where the key is the source and the value is the destination.

###Source###

The source can be specified as a simple string like:

{
  "foo": "bar"
}

You may specify properties deep within the source object to be copied to properties deep within the destination object by using dot notation in the mapping like:

{
  "foo": "bar.baz"
  , "bar.foo": "baz"
}

You may also specify array lookups within the source object to be copied to properties deep within the destination object by using [] notation in the mapping link:

{
  "[].foo": "bar[]"
  , "foo[].bar": "[]"
  , "foo[0].bar": "baz"
}

###Destination###

You may specify the destination as:

• String
• Object
• Array

####String####

When using string as destination you shall use as described above.

In order to utilize a source field more than once, utilize the key-transform syntax in the mapping link:

{
  "foo": [
    {
      key: "foo",
      transform: function (value) {
        return val + "_foo";
      }
    },
    {
      key: "baz",
      transform: function (value) {
        return val + "_baz"
      }
    }
  ],
  "bar": "bar"
}

####Object####

When using object as destination you need can use the following object:

{
  "key": (String)
  , "transform": (Function())
  , "default": (Function()|String|Number)
}

#####Methods#####

transform(sourceValue, sourceObject, destinationObject, destinationKey);

This function let you handle the sourceValue as you need;

default(sourceObject, sourceKey, destinationObject, destinationKey);

This function let you return a default value when the sourceValue is undefined or null.

####Array####

When using arrays as destination you can pass a string, object or another array (shorthand for object):

{
  "foo": ["bar", "baz"]
  , "bar": [{
    "key": "foo"
  }]
  , "baz": [["bar", null, "foo"]]
}

If you want to append items to an existing array, include a '+' after the []

{
  "sourceArray[]":{
    "key":"destination[]+",
    "transform": (val) => mappingFunction(val)
  },
  "otherSourceArray[]":{
    "key":"destination[]+",
    "transform:":(val) => mappingFunction(val)
  }
}
// Results in the destination array appending the source values
{
  "destination":[
    {/*Results from mapping function applied to sourceArray */},
    {/*Results from mapping function applied to otherSourceArray */},
  ]
}

The array shorthand for object is defined like:

[(Key(String))), (Transform(Function())), (Default(String|Number|Function()))]

###Null Values###

By default any source object null value is not mapped. If you want to allow this you may do so explicitly by including the post fix operator '?' to any destination key.

var original = {
  "sourceKey":null,
  "otherSourceKey":null
}
var transform = {
  "sourceKey":"canBeNull?",
  "otherSourceKey":"cannotBeNull"
}
var results = ObjectMapper(original, {}, transform);
// Results would be the following
{
  canBeNull:null
}

##Methods##

.merge(sourceObject[, destinationObject], mapObject);

Copy properties from sourceObject to destinationObject by following the mapping defined by mapObject

This function is also exported directly from require('object-mapper') (ie: var merge = require('object-mapper');)

• sourceObject is the object FROM which properties will be copied.
• destinationObject [OPTIONAL] is the object TO which properties will be copied.
• mapObject is the object which defines how properties are copied from sourceObject to destinationObject

.getKeyValue(sourceObject, key);

Get the key value within sourceObject, going deep within the object if necessary. This method is used internally but is exposed because it may be of use elsewhere with other projects.

• sourceObject is the object from which you would like to get a property/key value.
• key is the name of the property/key you would like to retrieve.

.setKeyValue(destinationObject, key, value);

Set the key value within destinationObject, going deep within the object if necessary.This method is used internally but is exposed because it may be of use elsewhere with other projects.

• destinationObject is the object within which the property/key will be set.
• key is the name of the property/key which will be set.
• value is the value of the property/key.

##Example##

var objectMapper = require('object-mapper');

var obj = {
  "sku" : "12345"
  , "upc" : "99999912345X"
  , "title" : "Test Item"
  , "description" : "Description of test item"
  , "length" : 5
  , "width" : 2
  , "height" : 8
  , "inventory" : {
    "onHandQty" : 12
  }
};

var map = {
  "sku": "Envelope.Request.Item.SKU"
  , "upc": "Envelope.Request.Item.UPC"
  , "title": "Envelope.Request.Item.ShortTitle"
  , "description": "Envelope.Request.Item.ShortDescription"
  , "length": "Envelope.Request.Item.Dimensions.Length"
  , "width": "Envelope.Request.Item.Dimensions.Width"
  , "height": "Envelope.Request.Item.Dimensions.Height"
  , "inventory.onHandQty": "Envelope.Request.Item.Inventory"
};

var result = objectMapper(obj, map);

/*
{
  Envelope: {
    Request: {
      Item: {
        SKU: "12345",
        UPC: "99999912345X",
        ShortTitle: "Test Item",
        ShortDescription: "Description of test item",
        Dimensions: {
          Length: 5,
          Width: 2,
          Height: 8
        },
        Inventory: 12
      }
    }
  }
};
*/

##Use case##

I use object-mapper's merge() method to map values from records returned from a database into horribly complex objects that will be eventually turned in to XML.

##License##

The MIT License (MIT)

Copyright (c) 2012 Daniel L. VerWeire

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.