ts-key-enum

A TypeScript string enum for compile-time safety when working with event.key.

Install

npm install ts-key-enum --save

yarn add ts-key-enum

Purpose

Tired of referencing keyboard keys with a string?

onKeyPress = (ev) => {

    // whoops, it's actually ArrowLeft!
    if (ev.key === 'LeftArrow') {
        ...
    }
}

Me too. With this module, you can do this instead (in a TypeScript file):

onKeyPress = (ev) => {

    // much better
    if (ev.key === Key.ArrowLeft) {
        ...
    }
}

Background

This is similar to the ts-keycode-enum module, but it provides an enum with string values that correspond with the event.key values instead of number values that correspond to the deprecated event.which and event.keyCode values.

Usage

To use this module, import the Key enum at the top of your TypeScript file:

import { Key } from 'ts-key-enum';

You can now use the enum value in place of key strings throughout the file:

// if (ev.key === 'Escape') { ... }
if (ev.key === Key.Escape) { ... }

See Key.enum.d.ts for a complete list of available keys. This file is auto-generated from the list of keys found at MDN: https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key/Key_Values.

What's included

The Key enum contains values for all standard non-printable keys such as "CapsLock", "Backspace", and "AudioVolumeMute". The enum does not contain values for printable keys such as "a", "A", "#", "é", or "¿", simply because the list of possible values is too vast to include in a single enum. To test for printable values, simply use a string comparison:

if (ev.key === 'é') { ... }

v2 vs v3

This package is published as two versions on NPM: v2.x and v3.x.

v2

v2.x defines the Key enum as a "basic" enum:

export enum Key { ... }

The end result is a JavaScript object that contains every enum value. You can see this object here: https://gitlab.com/nfriend/ts-key-enum/blob/v2/dist/js/Key.enum.js.

v3

v3.x defines the Key enum as a const enum:

export const enum Key { ... }

This allows the enum's definition to live entirely in the definition file https://gitlab.com/nfriend/ts-key-enum/blob/master/Key.enum.d.ts. Consumers can use this enum without including all of the enum's values in their own JavaScript bundle; only the values referenced in their code will be injected into their output file.

Which version should I use?

It's advisable to use v3.x unless you have a reason to use v2.x. Some reasons you may need to use v2.x:

• You are using this package as a JavaScript module (not a TypeScript module).
• You are using TypeScript < 1.4, which doesn't support const enum.
• You are using @babel/plugin-transform-typescript, which does not support const enum.
  • See #2 and https://github.com/babel/babel/issues/8741
  • Alternatively, use babel-plugin-const-enum to convert const enums to regular enum in your development environment, allowing you to reap the benefits of const enums in your production build (see https://www.npmjs.com/package/babel-plugin-const-enum#transform-removeconst-default).

Building

To build this module yourself, first install its dependencies using:

npm install

Next, run the scraper script (scrapeMDNForKeys.ts) using:

npm run scrape

This will overwrite Key.enum.d.ts with the updated list of keys found in MDN.

Verify that the enum builds without any TypeScript errors:

npm run build

Finally, make sure the enum passes all linters:

npm run lint

License

MIT