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  • License MIT

defines static object attributes using `Object.defineProperties`

Package Exports

  • static-props

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (static-props) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

static-props

defines static object attributes using Object.defineProperties

KLP

js-standard-style

Table Of Contents:

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