Enum Object

A JavaScript Enum object type that allows to easily create enums from arrays or objects, and offers developer-friendly interface.

Installation

$ npm install enum-object

Getting Started

Import as ES6 module

import Enum from 'enum-object'

Or require as CommonJs module:

const Enum = require('enum-object')

Usage:

import Enum from 'enum-object'

const statuses = new Enum({
  created: {
    value: 1,
    label: 'Created', // `label` and `color` props are optional extra data that could be whatever you need.
    color: 'grey'
  },
  inProgress: {
    value: 2,
    label: 'In Progress',
    color: 'yellow'
  },
  ready: {
    value: 3,
    label: 'Ready',
    color: 'brown'
  },
  done: {
    value: 4,
    label: 'Done',
    color: 'green'
  }
})

statuses.created
// { value: 1, label: "Created", color: "grey" }

statuses.created.valueOf()
// 1

statuses.created.toString()
// "1"

/* Due to valueOf method and coercion it's possible to do comparisons like this: */

statuses.ready == 3
// true

statuses.done > statuses.inProgress
// true

statuses.$enum.keys
// ["created", "inProgress", "ready", "done"]

statuses.$enum.values
// [1, 2, 3, 4]

statuses.$enum.items
// [
//    { value: 1, label: "Created", color: "grey" },
//   ...
//    { value: 4, label: "Done", color: "green" }
// ]

statuses.$enum.entries
// [
//    [ "created",  { value: 1, label: "Created", color: "grey" } ],
//   ...
//    [ "done",  { value: 4, label: "Done", color: "green" } ]
// ]


/* Since `keys`, `values`, `items`, `entries` props are always arrays it's very convenient
to use them together with map/filter/reduce/etc. array methods, like this: */

statuses.$enum.values.map(i => `${i.label} is ${i.color}`)
// ["Created is grey", "In Progress is yellow", "Ready is brown", "Done is green"]

statuses.$enum.hasKey('cancelled') // no such key
// false

statuses.$enum.hasValue(4)
// true

statuses.$enum.getByValue(1)
// { value: 1, label: "Created", color: "grey" }

Enum object creation

You can create an enum using either new keyword or create factory function. The result will be the same.

import Enum from 'enum-object'

// Using 'new' keyword
const colors = new Enum(['red', 'green', 'blue'])

// Using create method (factory function)
const colors = Enum.create(['red', 'green', 'blue'])

// { blue: "blue", green: "green": red: "red", $enum: {...} }

Input collection

It's possible to create an enum instance using either Array or Object as input argument.

Array input example:

const gender = new Enum(['MALE', 'FEMALE'])

// { MALE: "MALE", FEMALE: "FEMALE", $enum: {...} }

Object input example:

const gender = new Enum({
  male: 'm',
  female: 'f'
})

// { male: "m", female: "f", $enum: {...} }

Both Array and Object notations allow to use objects as items:

const gender = new Enum([
  { key: 'MALE', value: 'M' },
  { key: 'FEMALE', value: 'F' }
])
// or
const gender = new Enum({
  MALE: { value: 'M' },
  FEMALE: { value: 'F' }
})
// the result will be the same

When using object items, the value property of each item is required.

Enum keys

In case of object notation input object's keys always will be the enum keys.

As for Array notation, it depends on type of array items.

1. simple literal items (String, Number, Boolean) will be both key and value
2. for object items there should be key property defined for each input array item

All the examples below will result in the same set of enum keys:

const enumFromArrayOfStrings = new Enum(['MALE', 'FEMALE'])
console.log(enumFromArrayOfStrings.$enum.keys)
// ["MALE", "FEMALE"]

const enumFromArrayOfObjects = new Enum([
  { key: 'MALE', value: 'M' },
  { key: 'FEMALE', value: 'F' }
])
console.log(enumFromArrayOfObjects.$enum.keys)
// ["MALE", "FEMALE"]

const enumFromObject = new Enum({
  MALE: { value: 'M' },
  FEMALE: { value: 'F' }
})
console.log(enumFromObject.$enum.keys)
// ["MALE", "FEMALE"]

Notice that every enum instance created has $enum property, that contains a set of convenient methods and props. The full list of those can be found in $enum utils section.

Enum items and values

If the input collection contains objects like { value: 1, label: 'Apple', isTasty: true } then this object itself is an item, and it's value prop is a value.

If an input collection's item is primitive literal (String, Number, Boolean) than item is the same as value.

It's recommended to create enums with object notation and object values since it's the most flexible way and it's very easy to add additional props in the future without changing existing code.

Every item object is supplied by valueOf() and toString() methods (or you can provide them in the input collection), so that it's possible to do comparisons like this:

fruit.apple
// { value: 1, label: "Apple", isTasty: true }

fruit.apple.valueOf() // or +fruit.apple
// 1

fruit.apple == 1 // works only for Abstract Equality Comparison (==)
// true

fruit.apple <= 2
// true

$enum utils

An enum object instance has $enum prop, that contains a list of utility props and methods:

Property	Description
collection	Enum object without $enum prop
entries	Array of an enum's elements [key, value] pairs (the same as the result of Object.entries(enumInstance))
keys	Array of an enum's property names (the same as the result of Object.keys(enumInstance))
values	Array of an enum's values
items	Array of an enum's items
hasKey(key)	Boolean: Whether there an enum item with given key
hasValue(val)	Boolean: Whether there a corresponding enum value in the enum collection
getByValue(val)	Get enum item by given value

Other features

1. Enum instance is immutable, so that once enum is created it's not possible to change the items by mistake.
2. $enum utility prop is located next to the keys of the enum, but unlike them, $enum prop is not iterable (not enumerable).

Moreover, enum instance is iterable object, that means you can do for...of:

const statuses = new Enum(statusesInputObject)
for (const item of statuses) {
  console.log(item)
}
// { value: 1, label: "Created", color: "grey" }
// ...
// { value: 4, label: "Done", color: "green" }

Roadmap

• Extend $enum util object with own props and methods
• Define custom props for each enum item (on Enum instance creation)

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License

MIT