FlagSwappr

!TypeScript: Strict

Gates feature flags behind generational gaps.

Usage

FlagSwappr keeps track of whether features are enabled based on a current "generation".
It's based off the concept of game generations, such as Pokemon, where features are turned on or off in different releases.

$3

``typescript
const flagSwapper = new FlagSwappr({
generations: {
first: {
eggs: false,
},
second: {
eggs: true,
},
},
});
`

#### generation

Starting generation to enable, if not the first from generationNames.

`typescript
const flagSwapper = new FlagSwappr({
generation: "second",
generations: {
first: {
eggs: false,
},
second: {
eggs: true,
},
},
});

const { eggs } = flagSwapper.flags; // true
`

#### generationNames

Ordered names of the available generations, if not Object.keys(generations).
The first key in this string[] is used as the starting generation.

`typescript
const flagSwapper = new FlagSwappr({
generationNames: ["second", "first"],
generations: {
first: {
eggs: false,
},
second: {
eggs: true,
},
},
});

const { eggs } = flagSwapper.flags; // true
`

#### generations

Groups of feature settings, in order.
These represent the changes each generation made to the available feature flags.

#### Usage with TypeScript

FlagSwappr is templated across a TFlags type, where each of its flags are a Partial of that type.

The template is inferred from the constructor or can be specified manually.

`typescript
interface Flags {
eggs: boolean;
}

const flagSwapper = new FlagSwappr({
generations: {
first: {
eggs: false,
},
second: {
eggs: true,
},
},
});
`

---

$3

Getter for the generation-variant flags.
When a new generation is set, the internal representation is reset to an object with flags for what the current generation's state is for that generation.
Each member flag is equal the most "recent" generation setting, as defined by the generationNames order.

`typescript
const flagSwapper = new FlagSwappr({
generation: "third",
generationNames: ["first", "second", "third"],
generations: {
first: {
eggs: false,
},
second: {
eggs: true,
},
},
});

const { eggs } = flagSwapper.flags; // true
`

$3

Parameters:

- generationName: string: Generation for flag setting.

Sets flags to a generation.

`typescript
const flagSwapper = new FlagSwappr({
generation: "third",
generationNames: ["first", "second", "third"],
generations: {
first: {
eggs: false,
},
second: {
eggs: true,
},
},
});

flagSwapper.setGeneration("first");

const { eggs } = flagSwapper.flags; // false
`

Development

This repository is a portion of the EightBittr monorepo.
See its docs/Development.md for details on how to get started. 💖

$3

`shell
yarn run test
`

Tests are written in Mocha and Chai.
Their files are written using alongside source files under src/ and named *.test.ts?.
Whenever you add, remove, or rename a .test.t file under src/, watch will re-run yarn run test:setup to regenerate the list of static test files in test/index.html.
You can open that file in a browser to debug through the tests, or run yarn test:run` to run them in headless Chrome.