Fleg (https://en.wiktionary.org/wiki/fleg)

🎌 A simple but powerful feature flag handling solution.

• Control through Cookies.
• Control through Query String.
• Automatic value conversion.
• Browser support.
• NodeJS support.
• 0 dependency.
• Less than 1Kb (min+gz).

Installation

npm i fleg

Usage

Fleg is meant to be initialized ONLY ONCE!

During bootstrap stage (at the very beginning) of your application, import Fleg and define your initial flags.

import { Fleg } from 'fleg'

new Fleg({
    enableFoo: true,
    enableBar: false,
    stringFlag: 'string'
})

Further on at any other part of the application use the default import. It will be the Fleg instance you created previously.

import fleg from 'fleg'

fleg.enableFoo // true

API

Fleg is extending Map which means all Map APIs are available. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map

fleg.get('enableFoo')
fleg.set('enableFoo', false)
// ...

set(key: string|array|object, value: any, writeCookie?: boolean)

Fleg overrides the default set method of Map to extend its functionality.

// Passing true will write this flag to cookies
fleg.set('key', 'value', true)

// You may pass an "entries shaped" array
fleg.set([
    ['key', 'value'],
    ['foo', 'bar']
])

// Pass object
fleg.set({
    enableFoo: 1,
    enableBar: 2
})

delete(key: string)

Delete a flag. It'll also remove associated cookies.

fleg.delete('enableFoo')

reset()

Reset flags back to initial state (what was passed to the constructor).

resetFleg Query String option

For convenience, you can add resetFleg query string to your URL to remove all cookie flags.

e.g. yourdomain.com?resetFleg

Globals

For convenience, the created Fleg instance can be accessed on the global scope both in NodeJS and the Browser.

global.__fleg
window.__fleg

Layered control

Fleg has 3 layers in the following order of loading:

1. Initial flags: what is passed to the constructor.
2. Cookie flags: cookie flags will override initial flags.
3. Query String flags: will override all other flags AND will also set it as cookie, so it'll remain on next reload.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT