OLOO Factory Creator

This library allows for the creation of factory functions for objects implementing the OLOO pattern (Objects Linking to Other Objects). This is an alternative to classes for object orientation. See You Don't Know JS: this & Object Prototypes Chapter 6: Behavior Delegation for more information about the pattern.

Essentially this library allows a normal object notation syntax to be used for instantiation and inheritance instead of the horrible FunctionName.prototype.method = function ()... syntax or the ES6 class syntax and wraps the object creation up in a factory function. This has convenient functionality such as assigning properties automatically onto the new object and also hides the implementation details of how the object was created.

Installation

Node

Requires Node 4 due to requiring Object.assign().

npm install oloo-factory-creator

Browser

Download dist/create-factory.min.js or you can install with bower:

bower install oloo-factory-creator

Usage

In Node, import the createFactory function:

var createFactory = require('oloo-factory-creator');

In the browser, import via the script tag, which creates a global function called createFactory:

<script src="/path/to/dist/create-factory.min.js" type="text/javascript"></script>

Automatically assign properties into the created objects

The easiest method of creating objects is just to pass an object (or multiple objects) into the factory that will have their properties copied into the created object.

// The prototype for user objects
var User = {
    getName: function () {
        return this.name;
    }
};

var userFactory = createFactory(User);

// Create user objects with User as their prototype
var bob = userFactory({
    name: 'Bob'
});

var jim = userFactory({
    name: 'Jim'
});

// Accessing copied properties
console.log(bob.name); // Outputs "Bob"
console.log(jim.name); // Outputs "Jim"

// Calling prototyped methods
console.log(bob.getName()); // Outputs "Bob"
console.log(jim.getName()); // Outputs "Jim"

If you need to run some code after the object has been initialised with the passed in properties, you can specify a postInit() method in the prototype:

var User = {
    postInit: function() {
        console.log('My name is ' + this.name);
    }
};

var userFactory = createFactory(User);

// This outputs "My name is Bob"
var bob = userFactory({
    name: 'Bob'
});

Initialising created objects with an init() method

As an alternative, if an init() method is specified in the prototype, that will be used and properties will not be automatically assigned.

var User = {
    init: function (name) {
        this.name = name;
    },
    getName: function () {
        return this.name;
    }
};

var bob = userFactory('Bob');

console.log(bob.name); // Outputs "Bob"
console.log(bob.getName()); // Outputs "Bob"

Modules

With either of the above methods, if you're using modules, the recommended usage is to export the created factory method. For example, user.js could look like the following:

var createFactory = require('oloo-factory-creator');

var User = {
    ...methods
};

module.exports = createFactory(User);

And then imported into in another module thus:

var User = require('./user');

var user = User({
    name: 'Bob'
});

console.log(user.getName());

Inheritance

In OLOO there is no difference between inheritance and instantiation.

Testing

Simply clone the repository, run npm install and then run npm test. The tests are in tests/create-factory-spec.js.