D

Property descriptor factory

Originally derived from es5-ext package.

Defining properties with descriptors is very verbose:

var Account = function () {};
Object.defineProperties(Account.prototype, {
  deposit: { value: function () {
      /* ... */
    }, configurable: true, enumerable: false, writable: true },
  withdraw: { value: function () {
      /* ... */
    }, configurable: true, enumerable: false, writable: true },
  balance: { get: function () {
      /* ... */
    }, configurable: true, enumerable: false }
});

D cuts that to:

var d = require('d');

var Account = function () {};
Object.defineProperties(Account.prototype, {
  deposit: d(function () {
    /* ... */
  }),
  withdraw: d(function () {
    /* ... */
  }),
  balance: d.gs(function () {
    /* ... */
  })
});

By default, created descriptor follow characteristics of native ES5 properties, and defines values as:

{ configurable: true, enumerable: false, writable: true }

You can overwrite it by preceding value argument with instruction:

d('c', value); // { configurable: true, enumerable: false, writable: false }
d('ce', value); // { configurable: true, enumerable: true, writable: false }
d('e', value); // { configurable: false, enumerable: true, writable: false }

// Same way for get/set:
d.gs('e', value); // { configurable: false, enumerable: true }

Installation

$ npm install d

To port it to Browser or any other (non CJS) environment, use your favorite CJS bundler. No favorite yet? Try: Browserify, Webmake or Webpack

Other utilities

autoBind(obj, props) (d/auto-bind)

Define methods which will be automatically bound to its instances

var d = require('d');
var autoBind = require('d/auto-bind');

var Foo = function () { this._count = 0; };
Object.defineProperties(Foo.prototype, autoBind({
  increment: d(function () { ++this._count; });
}));

var foo = new Foo();

// Increment foo counter on each domEl click
domEl.addEventListener('click', foo.increment, false);

lazy(obj, props) (d/lazy)

Define lazy properties, which will be resolved on first access

var d = require('d');
var lazy = require('d/lazy');

var Foo = function () {};
Object.defineProperties(Foo.prototype, lazy({
  items: d(function () { return []; })
}));

var foo = new Foo();
foo.items.push(1, 2); // foo.items array created and defined directly on foo

Tests

$ npm test