Value Object JS

The Value Object is a usefull, well known design pattern in a lot of languages. JavaScript is not one of them, until now. This plugin allows you to create your own 'Data types' as value object in order to better structure your application logic.

Installation

Bower

bower install --save value-object-js

<script src="/bower_components/value-object-js/dist/value-object.min.js"></script>
<script>
	var Email = ValueObject.define('Email', function() { ... });
	
	// ...
</script>

Besides the value-object.js file, this package also provides a set of predefined value objects like DateRang, Email, URL, YoutubeVideoURL and more. This library can be loaded on its own (value-object-library.min.js) or as part of the main file (value-ibject.with-library.min.js).

NPM

npm install --save value-object-js

var ValueObject = require('value-object-js');

var Email = ValueObject.define('Email', function() { ... });

// ...

Usage

Define a value object

A value object only requires a name and a validation function testing the passed value.

var Email = ValueObject.define('Email', function(value) {
	return /(.+)@(.+){2,}\.(.+){2,}/.test(value);
});

Using the defined value object is now as simple as instantiating any object using the new keyword. Defined value objects can also be found in the library.

var customerEmail = new Email('example.domain.com'); // Throws InvalidArgumentException

var customerEmail = new Email('[email protected]'); // Works!

var customerEmail = new ValueObject.Library.Email('[email protected]'); // Works!

The value object can now be handled like you would a String object.

console.log(customerEmail); // logs an object

console.log('Hi! Mail me at: ' + customerEmail); // logs 'Hi! Mail me at: [email protected]'

Comparing value objects

Objects in javascript are equal on identity, not on value. Value objects, however, are equal on value and can be compared with strict equality. They even can be tested with instanceOf.

var email1 = new Email('[email protected]');
var email2 = new Email('[email protected]');

console.log(email1 === email2); // logs true
console.log(email1 instanceof Email); // logs true

Adding methods

An email address is basicly a string, so it would be helpful if we could use the same methods. This can be done by specifying which data type (or other value object!) should be extended in the definition. You can also add your own methods.

var Email = ValueObject.create('Email', {

	// Extends all methods from String (like substr, split, match, etc.)
	extends: 'String',
	
	validate: function(value) { // your validation here };
	
	getDomainPart: function() {
		return this.value.split('@').pop();
	}
});

var email = new Email('[email protected]');

console.log(email.substr(0, 7)); // logs 'example'
console.log(email.getDomainPart()); // logs 'domain.com'

Documentation

For full documentation see http://dev.tsoffereins.com/value-object-js/documentation/.

Support

You can reach me via Twitter: @tsoffereins

Please file issues here at GitHub.