frosty v0.0.1

frosty

Introduction

Define frozen properties on objects:

• a frozen property can be set to an non-undefined value just once
• any further attempts to change its value will throw an Error

Install

Via NPM.

npm install --save frosty

Usage

Canonical example of an immutable type:

import frosty from 'frosty'

class ImmutableType {
  constructor(property1, property2) {
    this.property1 = property1
    this.property2 = property2
  }
}

frosty.freeze(ImmutableType.prototype, 'property1', 'property2')

undefined isn't a valid value for a frozen property:

// throws "'property2' should be defined"
let immutable_type = new ImmutableType('my_property1', undefined)

Frozen properties are read-only, and can only be set once:

let immutable_type = new ImmutableType('my_property1', true)

immutable_type.property1 // 'my_property1'
immutable_type.property1 = 'another_property1' // "throws 'my_property1' is immutable"

See the tests for more examples.

Development

In ES6 & Babel.

Transpile:

$ node_modules/.bin/gulp build

Test:

$ sudo chmod +x test.js
$ npm test

LICENSE

MIT © 2015, Victor Alvarez