Go Constant

Store values that should remain unchanged in constant properties with ease. Similar to using the const declaration, it creates a read-only reference to a value (configurable: false, writable: false, enumerable: true), however it does not make the stored value immutable. While the constant properties are protected from reassignment and reconfiguration, new properties can still be added. If you want to finalise an object and prevent extension, use Object.freeze().

• version: 1.1.0
• license: GNU LGPLv3

Installation

npm i go-constant

or

yarn add go-constant

Importing

ES6

import Constant from "go-constant";

Node

const Constant = require("go-constant");

Browser

<script src="dist/go-constant.min.js"></script>

Usage

Simple

const RED = Constant("#FF0000", "Red");

console.log(RED.value);            // => "#FF0000"
console.log(RED.valueOf());        // => "#FF0000"
console.log(RED.name);            // => "Red"

Enum-like

const options = { valueOf: "dayOfWeek", saveInstances: true };

const Day = Constant.newType("Day", ["dayOfWeek", "name", "shortName"], options);

Object.assign(Day, {
    MONDAY : Day(1, "Monday", "Mon"),
    TUESDAY : Day(2, "Tuesday", "Tue"),
    WEDNESDAY : Day(3, "Wednesday", "Wed"),
    THURSDAY : Day(4, "Thursday", "Thu"),
    FRIDAY : Day(5, "Friday", "Fri"),
    SATURDAY : Day(6, "Saturday", "Sat"),
    SUNDARY : Day(7, "Sunday", "Sun")
});

console.log(Day.MONDAY.dayOfWeek);  // => 1
console.log(Day.MONDAY.valueOf());  // => 1
console.log(Day.MONDAY.name);       // => "Monday"
console.log(Day.MONDAY.shortName);  // => "Mon"
console.log(Day.instances.length);  // => 7

Documentation

Table of Contents

• Constant
  • Parameters
  • Examples
• newType
  • Parameters
  • Examples

Constant

Creates a wrapper object which has constant value and name properties.

Parameters

• value any The value of the constant.
• name string The name of the constant.

Examples

const RED = Constant("#FF0000", "Red");

console.log(RED.value);          // => "#FF0000"
console.log(RED.valueOf());      // => "#FF0000"
console.log(RED.name);           // => "Red"

Meta

• since: 1.0.0

newType

Creates a new constant type constructor.

Parameters

• name string The name of the constructor.
• propNames Array<string> The names of the constructor parameters which will be constant properties.

• options Object? Constructor options.

  • options.validate function? The constructor parameter validator.
  • options.valueOf (function | string)? The name of the property to return as the value of the instance or the function to use to return the value of the instance.
  • options.saveInstances boolean? Whether to save instances or not. The instances are saved in an array, {ConstantType}.instances.

Examples

const Day = Constant.newType("Day", ["dayOfWeek", "name", "shortName"], { 
   valueOf: "dayOfWeek", 
   saveInstances: true 
});

const MONDAY = Day(1, "Monday", "Mon");

console.log(MONDAY.dayOfWeek);   // => 1
console.log(MONDAY.valueOf());   // => 1
console.log(MONDAY.name);        // => "Monday"
console.log(MONDAY.shortName);   // => "Mon"
console.log(Day.instances);      // [ Day { dayOfWeek: 1, name: "Monday", shortName: "Mon" } ]

Returns function The new constant type constructor.

Meta

• since: 1.1.0

v1.1.0

2023-01-23

• Added the newType function to allow creating new constant types.

v1.0.0

2022-12-06

• Initial release