extendable-base

extendable-base: Simple library for setting up Javascript classes

Leverages Backbone.extend semantics for defining subclasses in a generic way, making it straightforward to set up javascript class hierarchies.

As a convenience, adds logic so that the default constructor for the Base class calls initialize function on all classes in the inheritance chain passing the same arguments to each class.

Basic Usage

var Base = require('base-extend');

var MyClass = Base.extend({
    initialize: function(name) {
        this.name = name;
    },

    whoami: function() {
        console.log("I am", this.name);
    }
});

console.log(new MyClass('joe').whoami());
// 'I am joe'

Inheritance

Simple inheritance chains work as well, calling initialize for all classes in the chain:

var Animal = Base.extend({
    initialize: function(type) {
        this.classname = "Animal";
        this.type = type;
    },

    ident : function() {
        return 'I am an ' + this.classname + ': ' + this.type;
    },

    legs : function() {
        return 'I have ' + this._legs + ' legs';
    }
});

var FourLegged = Animal.extend({
    // Initialize is called for all classes
    initialize : function(type) {
        this._legs = 4;
    }
});

var dog = new FourLegged('dog');

console.log(dog.ident());
// 'I am an Animal: dog'

console.log(dog.legs());
// 'I have 4 legs'

Extending existing types

You can use Base.extends to subclass an existing Javascript type, for example to define custom Error subclasses:

var BaseError = Base.inherits(Error, {
    default_status: 500,

    initialize: function(message, status) {
        Error.call(this, message);

        this.message = message || this.default_message || "";
        this.status = status || this.default_status;
    },

    toJSON: function() {
        return {status: this.status, message: this.message};
    }
});

var NotFoundError = BaseError.extend({
    default_status: 404,
    default_message: "Bad Request"
});

var BadRequestError = BaseError.extend({
    default_status: 400,
    default_message: "Not Found"
});

console.log(new BadRequestError().toJSON());
// { status: 400, message: 'Not Found' }

console.log(new BadRequestError("Invalid request").toJSON());
// { status: 400, message: 'Invalid request' }

console.log(new BadRequestError("Unauthorized", 401).toJSON());
// { status: 401, message: 'Unauthorized' }

console.log(new NotFoundError().toJSON());
// { status: 404, message: 'Bad Request' }