static-props

defines static object attributes using Object.defineProperties

Table Of Contents:

• Installation
• Usage
• Annotated source
• License

Installation

With npm do

npm install static-props --save

Usage

Let's create a classic Point2d class and add constant attributes.

'use strict'

var staticProps = require('static-props')

class Point2d {
  constructor (x, y, label) {
    // Suppose you have few static attributes in your class.
    const color = 'red'

    // Add constant attributes quickly.
    staticProps(this)({label, color})

    // Add enumerable attributes.
    var enumerable = true
    staticProps(this)({x, y}, enumerable)
  }
}

After instantiating the class, we can check that its props cannot be changed.

var p = new Point2d(1, 2)

// Trying to modify a static prop will throw as you expect.
p.label = 'B'
// TypeError: Cannot assign to read only property 'label' of #<Point2d>

Attributes x, y were configured to be enumerable

console.log(p) // Point2d { x: 1, y: 2 }

If you want to add a static attribute class, you can also do

staticProps(Point2d)({ dim: 2 })

so you can access it with

console.log(Point2d.dim) // 2

Annotated source

API is staticProps(obj)(props[, enumerable])

/**
 * @param {Object} obj
 * @returns {Function}
 */

function staticProps (obj) {
  /**
   * @param {Object} props
   * @param {Boolean} [enumerable]
   */

  return function (props, enumerable) {

Since static is a reserved keywork, let's use statik

    var statik = {}

Add every prop to obj as not writable nor configurable, i.e. static

    for (var propName in props) {
      var propValue = props[propName]

      statik[propName] = {
        value: propValue,
        configurable: false,
        enumerable: enumerable,
        writable: false
      }
    }

    Object.defineProperties(obj, statik)
  }
}

Export function

module.exports = staticProps

License

MIT