lighter-type

The lighter-type module is a prototypal inheritance utility with better performance than similar inheritance utilities.

It supports:

• Constructors
• Prototypal inheritance
• Multiple inheritance
• Non-enumerable property definitions

Installation

From your project directory, install and save as a dependency:

npm install --save lighter-type

Usage

The lighter-type module outputs a constructor with several methods.

• Type.extend(prototypeProps[, constructorProps])
• Type.init(object[, overwrite][, args])
• Type.decorate(object[, map][, overwrite])
• Type.include(type[, overwrite])
• Type.is(type)
• Type.has(type)
• Type.hide(object, key, value)

Type.extend([constructor], [prototypeProps], [constructorProps])

Define and return a sub type of the Type object, with a prototype decorated with optional prototypeProps (a map of additional prototype properties) and optional constructorProps (a map additional type properties. The sub type itself also inherits the properties of its super type (such as the extend method).

When the prototypeProps argument includes a property called init, it is used as the constructor for the sub type rather than being added as a prototype property.

var Type = require('lighter-type')
 
// Construct a new person with a name.
var Person = Type.extend(function Person (name) {
  this.name = name
}, {
  // Give a person a default salutation of "Hello".
  salutation: 'Hello',
 
  // Greet a person with their defined salutation.
  greet: function () {
    console.log(this.salutation + ', ' + this.name + '!')
  }
}, {
  // Identify this type, if asked.
  getTypeName: function () {
    return 'Person'
  }
})
 
// Make a Friend sub type by extending the Person type.
var Friend = Person.extend({
  // Be a bit more informal with friends.
  salutation: 'Hi'
}, {
  // Identify this type, if asked.
  getTypeName: function () {
    return 'Friend'
  }
})
 
// Instantiate Bob, and greet him.
var bob = new Person('Bob')
bob.greet()
//> "Hello, Bob!"
 
// Instantiate Joe, and greet him.
var joe = new Friend('Joe')
joe.greet()
//> "Hi, Joe!"
 
// Make sure a Friend is a Friend.
console.log(Friend.getTypeName())
//> "Friend"

Each type's prototype has _super property which references its parent prototype, and each type has a _super property which references its parent type.

var Type = require('lighter-type')
 
var Robot = Type.extend({
  bend: function (object) {
    object.isBent = true
  }
})
 
var Bender = Robot.extend({
  bend: function (object) {
    this._super.bend(object)
    console.log('Bite my shiny metal ass.')
  }
})
 
var beam = {}
var bender = new Bender()
bender.bend(beam)
//> Bite my shiny metal ass.
 
console.log(beam.isBent)
//> true

Type.init(object[, overwrite][, args])

Decorate an object with the prototype of a Type, and call its constructor on the object with an args array, unless args is false, in which case the constructor will be skipped.

Any object that extends Type (such as lighter-emitter) will inherit Type.init and other Type methods.

// The `lighter-emitter` module extends `lighter-type`.
var Emitter = require('lighter-emitter')
 
// Make the `console` object into an emitter.
Emitter.init(console)
 
console.on('hi', function (name) {
  console.log('Hi, ' + name + '!')
})
 
console.emit('hi', 'Sam')
//> Hi, Sam!

Type.decorate(object[, map][, overwrite])

Decorate an object with a map of additional properties (or overriding properties if overwrite is truthy). If the map is not specified, the Type prototype will decorate the object prototype instead.

var Type = require('lighter-type')
 
// Add a few methods to the Array object's prototype.
Type.decorate(Array.prototype, {
  first: function () {
    return this[0]
  },
  last: function () {
    return this[this.length - 1]
  },
  sum: function () {
    var s = 0
    for (var i = 0, l = this.length; i < l; i++) {
      s += this[i]
    }
    return s
  }
})
 
// Create a plain old array of numbers.
var a = [1, 2, 3]
 
console.log(a.first())
//> 1
 
console.log(a.last())
//> 3
 
console.log(a.sum())
//> 6

Type.include(type[, overwrite])

Implement multiple inheritance by decorating one Type's prototype with the prototype properties of another.

var Type = require('lighter-type')
 
// A vehicle might work on land or water.
var Vehicle = Type.extend({
 
  // Return isLandVehicle as a boolean.
  worksOnLand: function () {
    return !!this.isLandVehicle
  },
 
  // Return isWaterVehicle as a boolean.
  worksOnWater: function () {
    return !!this.isWaterVehicle
  }
 
})
 
// A car is a land vehicle.
var Car = Vehicle.extend({
  isLandVehicle: true
})
 
// A boat is a water vehicle.
var Boat = Vehicle.extend({
  isWaterVehicle: true
})
 
// A hovercraft is also a vehicle.
var Hovercraft = Vehicle.extend({})
 
// A hovercraft includes the functionality of a Car and a Boat.
Hovercraft.include(Car)
Hovercraft.include(Boat)
 
// Create a new Hovercraft.
var hovercraft = new Hovercraft()
 
console.log(hovercraft.worksOnLand())
//> true
 
console.log(hovercraft.worksOnWater())
//> true

Type.is(type)

Check whether this Type is descended from another Type.

var Foo = Type.extend({})
var Bar = Foo.extend({})
var Baz = Bar.extend({})
 
console.log(Baz.is(Foo))
//> true
 
console.log(Foo.is(Baz))
//> false

Type.has(type)

Check whether this Type has acquired the functionality of another type via the extend method or the include method.

var Type = require('lighter-type')
 
// Create an object with a visible (i.e. enumerable) method.
var object = {
  visible: function () {
    console.log('I am visible.')
  }
}
 
// Add a non-enumerable property called "hidden".
Type.hide(object, 'hidden', function () {
  console.log('I am hidden.')
})
 
// Verify that the "hidden" method exists.
object.hidden()
//> "I exist."
 
// Verify that only the "visible" method is enumerable.
for (var key in object) {
  console.log(key)
}
//> "visible"

Type.hide(object, key, value)

Create a property of object named key with value value, and "hide" it by making it non-enumerable.

var Type = require('lighter-type')
 
// Create an object with a visible (i.e. enumerable) method.
var object = {
  visible: function () {
    console.log('I am visible.')
  }
}
 
// Add a non-enumerable property called "hidden".
Type.hide(object, 'hidden', function () {
  console.log('I am hidden.')
})
 
// Verify that the "hidden" method exists.
object.hidden()
//> "I exist."
 
// Verify that only the "visible" method is enumerable.
for (var key in object) {
  console.log(key)
}
//> "visible"

More on lighter-type...

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