jsprops

Properties for JavaScript Prototypes.

Library provides class based properties that can be bound directly to a prototype, which reduces redundancy of coping the same property among instances.

Additionally, we can easily inherit from Properties class, extending it by our own getters/setter logic.

Default property's value is inited in a lazy way, first time it's accessed.

Example

{ property } = require 'jsprops'
 
class Klass
    foo: property 'foo'
    bar: property('bar', null, 'def_value')
    baz: property('baz',
        set: (set, val) ->
            set val.replace /a/, 'b'
    )
    woof: property('woof',
        init: (set) -> set null
        get: (get) -> get().replace /z/, 'b'
        set: (set, val) ->
            set val.replace /a/, 'b'
        'def_value'
    )
 
instance = new Klass
instance.foo() # returns 'foo' 
instance.foo 'bar'
instance.foo() # returns 'bar' 

Repeated name in a declaration is required by the design.

Signals

Signals are extended properties, adding nice bindings to an event emitter. An interesting feature is the support for inheritance. You can define an overriding signal in a child class, while still preserving listener defined in the super class. The only condition is the requirement of using @signal instead of signal (needed for a prototype chain resolution).

For signals, set is an emit and get returns temp object with binding functions (on, once) and an init function. All of them can be defined inside a declaration. They are also compatible with EventEmitter2Async (with callback and after/before events). Additionally, each signal needs to be initialized (manually or using SignalsMixin#initSignals).

Example

{
    signal
    SignalsMixin
} = require 'jsprops'
 
# This example actually lacks event emitter, but mixins are out of it's scope. 
class Klass extends SignalsMixin
    foo: signal('foo',
        on: -> console.log 'klass1'
    )
 
    on: -> # forward to a composed event emitter 
    emit: -> # forward to a composed event emitter 
 
class Klass2 extends Klass
    constructor: ->
        @initSignals()
 
    foo: @signal('foo',
        on: -> console.log 'klass2'
    )
 
instance = new Klass
instance.foo().on ->
    console.log 'listener'
instance.foo() # prints 'klass1', 'klass2', 'listener' 

JavaScript examples

property = require('jsprops').property
 
function Klass() {}
 
Klass.prototype.foo = property('foo')
Klass.prototype.bar = property('bar', null, 'def_value')
Klass.prototype.baz = property('baz', {
    set: function(set, val) {
        set(val.replace(/a/, 'b'))
    }
})
Klass.prototype.baz = property('woof', {
        init: function(set) {
            set(null)
        },
        get: function(get) {
            return get().replace(/z/, 'b')
        },
        set: (set, val) ->
            set(val.replace(/a/, 'b'))
    }, 'def_value'
)

Install

npm install jsprops

Contracts

This library provides contracts (read - runtime type checking) based on contracts.coffee library. There's a special build for that, so don't worry when using the default one. To make it work, a flag global.contracts is needed.