@dalokey/enumerator

A container for a finite set of elements that provides various enumeration functionality.

Installation

Listed on npm, and can be installed by running:

npm i -S @dalokey/enumerator

Summary

Enumeration is commonly used to refer to a finite set of elements in a collection.

This package provides a few functions that can be very helpful when handling the elements in the collection.

Furthermore, Unlike the typeScript enum, when implementing this package's Enum class, it is possible to extend the class by adding functions and properties that can handle very specific cases. This encourages a domain driven development (DDD) approach as the logic for an enum can be contained in a specific domain.

Usage

To better understand the usage of this package, an enumeration of colour codes will be used as an example.

First create the colour class, which will inherit the Enum<T, TValue> class. T is the Colour Enum class type itself, and TValue is the type for the Value property of each enum element. Therefore,class Colour extends Enum<Colour, number> will contains a list of Colour enums that have numbers as values.

class Colour extends Enum<Colour, number> {
    static Red: Colour = new Colour("red", 1001);
    static Blue: Colour = new Colour("blue", 1002);
    static Green: Colour = new Colour("Green", 1003);

    // custom features, including functions and properties
}

As shown on this code snippet Colour is the Enum class, and to add an enum element, a public static property is instantiated with name and value. It is important for these enums to be static.

Now it is possible to use all of this package's features.

These features are separated into three types: Element, Enumerator, and Custom features

Element features

The element features are accessed directly from the enum elements. They include:

.Name and .Value - getting the name and value of enum element

These are just properties to get the Name and Value of an enum element:

let name = Colour.Red.Name; // "red"
let value = Colour.Red.Value; // 1001

.equals(Enum) - check if an enum element is equal to another enum element

The equal() function is used to check if the enum element is equal to another. This can be very handy in many cases. The example below shows a function returning a value and then we check if it is the expected value.

let getFavoriteColour = (e: number): Colour => {
    if (e <= 50) {
        return Colour.Red
    } else {
        return Colour.Blue
    }
}

let myFavoriteColour = getFavoriteColour(8);

let isRedMyFavoriteColour = Colour.Red.equals(myFavoriteColour); // true

Enumerator features

All the enumerator features are static and can be accessed from the Enumerator class provided by this package.

Enumerator.getAll(Enum) - getting all the enum elements

The getAll() function is used to get an array containing all the static enum elements.

let listOfColourEnums = Enumerator.getAll(Colour); // [Colour{Name: 'red', Value: 1001}, Colour{Name: 'blue', Value: 1002}, ...]

Enumerator.getByName(Enum, "name", defaultEnum) - getting an enum element by name

The getByName() function is used to get an enum element by its name. This will return the first enum element it finds if there are more than one with the same name.

let blueEnum = Enumerator.getByName(ColourType, "blue"); // Colour{Name: 'blue', Value: 1002}

Enumerator.getByValue(Enum, TValue, , defaultEnum) - getting an enum element by value

The getByValue() function is used to get an enum element by its value. This will return the first enum element it finds if there are more than one with the same value.

let blueEnum = Enumerator.getByValue(ColourType, 1002); // Colour{Name: 'blue', Value: 1002}

Enumerator.isNameValid(Enum, "name") - check if an enum element exists with the provided name

The isNameValid() function is used to check if an enum element with the provided name exists

let blueEnum = Enumerator.isNameValid(ColourType, "blue"); // true

Enumerator.isValueValid(Enum, TValue) - check if an enum element exists with the provided value

The isValueValid() function is used to check if an enum element with the provided value exists

let blueEnum = Enumerator.isValueValid(ColourType, 1002); // true

Custom features

As the name suggests, custom features are created in the Enum class or inherited from a base class. This encourages a domain driven development (DDD) approach as the logic for this enum class can be contained in a specific domain.

The following shows some features added to the Colour2 enum class.

class Colour2 extends Enum<Colour2, string> {
    static White: Colour2 = new Colour2("red", 1001);
    static Blue: Colour2 = new Colour2("blue", 1002);
    static Green: Colour2 = new Colour2("Green", 1003);

    getName = (): string => {
        return this.Name;
    }

    static favoriteColour = (e: number): Colour2 => {
        if (e <= 50) {
            return Colour2.Red
        } else {
            return Colour2.Blue
        }
    }
}

And to call the custom method, the following is used

let myFavoriteColour = Colour2.favoriteColour(200); // Colour2{Name: 'blue', Value: 1002}
let nameOfColourRed = Colour2.Red.getName(); // "red"

Please feel free to suggest any features and let us discuss how to evolve this package together!