json-map-transform

A lighweight Node library that transforms a json object or an array of json objects based on tranformation template.

Installation

Using npm:

npm i --save json-map-transform

Usage

Template

Single object transformation

Array transformation

---

Template

Key: Each key property in the template object describes the path to the property in the output object. This is where the value in path of the input object will be mapped to.

Path: Is the path to the property in the input object that will be mapped to the template key. It can also be an array of possible paths in case the objects doesn't follow an exact pattern.

Transform: Is a callback that can be used to transform the current property. It receives two parameters: (property, originalObject).

Default: In case a path does not exists in the input object or the value returned by transform is undefined, the default value will be used.

OmitValues: Sometimes it is necessary to ignore values on the transformation (ex: undefined, empty string or other values depending on a business rule). With the omitValues, it is possible to define an array of values that should be ignored on the transformation. The output object will not have the associated key.

Template example:

const template = {
	title: {
		path: 'name',
		transform: (val) => val.toUpperCase()
	},
	label: {
		path: ['category', 'categories'],
		omitValues: ['', undefined, 'ERROR']
	},
	vendor: {
		path: 'meta.vendor',
		default: 'No vendor'
	},
	'meta.photos': {
		path: 'photos',
		transform: (val) => val.map(photo => photo.photoUrl)
	},
	'meta.id': {
		path: 'code'
	}
}

This template will work like this:

from	to	transform
name	title	toUpperCase()
[category, categories]	label
meta.vendor	vendor
photos	meta.photos	photo.photoUrl
code	meta.code

Single object transformation

const transform = require('json-map-transform');

//The json objects to be transformed
const product1 = {
	name: 'Hello world',
	code: 'BOOK01',
	category: 'books',
	price: '200',
	photos: [ 
		{ title: 'photo1', photoUrl: 'http://photo1.jpg', isCover: true },
		{ title: 'photo2', photoUrl: 'http://photo2.jpg' }
	],
	meta: {
		vendor: 'Author name'
	}
};

const product2 = {
	name: 'My Digital Product',
	code: 'DIGITAL01',
	category: 'digital',
	price: '500',
	photos: [ 
		{ title: 'photo3', photoUrl: 'http://photo3.jpg', isCover: true },
		{ title: 'photo4', photoUrl: 'http://photo4.jpg' }
	],
	meta: {
		vendor: 'Global Digital'
	}
};

convertedJson = transform(product1, template);

//Output object
{
    "title": "HELLO WORLD",
    "label": "books",
    "vendor": "Author name",
    "meta": {
        "photos": [
            "http://photo1.jpg",
            "http://photo2.jpg"
        ],
        "id": "BOOK01"
    }
}

You ca also use an optional callback to be executed after the transformation

const afterTransform = (element) => Object.assign({}, element, {
	categoryCode: element.label == 'books' ? 101 : 102
});

transform(product1, template, afterTransform);

// Output json
{
    "title": "HELLO WORLD",
    "label": "books",
    "vendor": "Author name",
    "meta": {
        "photos": [
            "http://photo1.jpg",
            "http://photo2.jpg"
        ],
        "id": "BOOK01"
    },
    "categoryCode": 101
}

Array transformation

// The afterTransform callback is also optional
transform([product1, product2], template, afterTransform);


[
    {
        "title": "HELLO WORLD",
        "label": "books",
        "vendor": "Author name",
        "meta": {
            "photos": [
                "http://photo1.jpg",
                "http://photo2.jpg"
            ],
            "id": "BOOK01"
        },
        "categoryCode": 101
    },
    {
        "title": "MY DIGITAL PRODUCT",
        "label": "digital",
        "vendor": "Global Digital",
        "meta": {
            "photos": [
                "http://photo3.jpg",
                "http://photo4.jpg"
            ],
            "id": "DIGITAL01"
        },
        "categoryCode": 102
    }
]

The afterTransform callback is called after each element tranformation.