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object-mapper

object-mapper#

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About##

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##

A mapping object key is the source key and the value is the key on the destination object the value is mapped to.

Source###

The source key can be specified as a simple string:

{
  "foo": "bar" //map src.foo to dest.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 key:

{
  "foo": "bar.baz", //map src.foo to dest.bar.baz 
  "bar.foo": "baz" //map src.bar.foo to dest.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:

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

Destination###

You may specify the destination as:

  • String
  • Object
  • Array

String####

When using a String as the destination, use the method described above.

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

var objectMapper = require('object-mapper');
 
var map = {
  "foo": [
    {
      key: "foo",
      transform: function (value) { 
        return value + "_foo";
      }
    },
    {
      key: "baz",
      transform: function (value) {
        return value + "_baz";
      }
    }
  ],
  "bar": "bar"
};
 
var src = {
    foo: 'blah',
    bar: 'something'
};
 
var dest = objectMapper(src, map);
 
// dest.foo: 'blah_foo' 
// dest.baz: 'blah_baz' 
// dest.bar: 'something'  

Object####

Using an Object as the destination:

{
  "key": (String),
  "transform": (Function()),
  "default": (Function()|String|Number)
}
Methods#####
transform(sourceValue, sourceObject, destinationObject, destinationKey);

Specify the mapping of a sourceValue as you need;

default(sourceObject, sourceKey, destinationObject, destinationKey);

Specify a default return value when the sourceValue is undefined or null.

Array####

When using an Array as the destination you can pass a String, an 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, append 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 the mapping function applied to sourceArray */},
    {/*Results from the mapping function applied to otherSourceArray */},
  ]
}

The Array shorthand for an Object:

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

Null Values###

By default null values on the source Object is not mapped. You can override this 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 src = {
  "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 dest = 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 the 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.