FLU

Flu is a tiny, dependency‑free, chainable terminal styling library.

• Chainable styles, nested styling support, multiple args
• Full 16/bright colors, background colors, modifiers
• RGB and HEX truecolor support
• Simple plugin API to add custom styles

Install

npm install @invboyz/flu

Quick Start

// ESM/TypeScript
import flu from '@invboyz/flu';

// CommonJS
const flu = require('@invboyz/flu');

console.log(flu.blue('Hello world!'));

// Combine styled and normal strings
console.log(flu.blue('Hello') + ' World' + flu.red('!'));

// Chain styles
console.log(flu.blue.bgRed.bold('Hello world!'));

// Multiple arguments
console.log(flu.blue('Hello', 'World!', 'Foo', 'bar', 'biz', 'baz'));

// Nest styles
console.log(flu.red('Hello', flu.underline.bgBlue('world') + '!'));

// Nest same-type styles
console.log(
  flu.green(
    'I am a green line ' +
    flu.blue.underline.bold('with a blue substring') +
    ' that becomes green again!'
  )
);

// Template literal
console.log(`
CPU: ${flu.red('90%')}
RAM: ${flu.green('40%')}
DISK: ${flu.yellow('70%')}
`);

// Truecolor
console.log(flu.rgb(123, 45, 67).underline('Underlined reddish color'));
console.log(flu.hex('#DEADED').bold('Bold gray!'));

API

• Callables: every style builder is callable: flu.blue('text')
• Chainable: flu.red.bold.underline('text')
• Nesting safe: inner style closes are restored automatically
• Multiple arguments: flu.cyan('a', 1, true) → a 1 true

Colors (foreground)

• Basic: black, red, green, yellow, blue, magenta, cyan, white, gray/grey
• Bright: blackBright, redBright, greenBright, yellowBright, blueBright, magentaBright, cyanBright, whiteBright

Background colors

• Basic: bgBlack, bgRed, bgGreen, bgYellow, bgBlue, bgMagenta, bgCyan, bgWhite, bgGray/bgGrey
• Bright: bgBlackBright, bgRedBright, bgGreenBright, bgYellowBright, bgBlueBright, bgMagentaBright, bgCyanBright, bgWhiteBright

Modifiers

• reset, bold, dim, italic, underline, inverse, hidden, strikethrough

Truecolor

• rgb(r, g, b) – 0..255
• bgRgb(r, g, b)
• hex('#RRGGBB' | '#RGB')
• bgHex('#RRGGBB' | '#RGB')

Plugin API

Extend Flu at runtime with custom styles (and extend the types via module augmentation if desired).

import flu from '@invboyz/flu';

// 1) Register a simple open/close style
flu.registerStyle('frame', '\u001B[51m', '\u001B[54m');
console.log(flu.frame('framed!'));

// 2) Register a dynamic style
flu.registerDynamicStyle('hsl', (h: number, s: number, l: number) => {
  // convert to RGB (demo: fake; plug your conversion)
  const [r, g, b] = [h % 255, s % 255, l % 255];
  return { open: `\u001B[38;2;${r};${g};${b}m`, close: '\u001B[39m' };
});
console.log(flu.hsl(200, 60, 50)('ocean'));

// 3) Bulk extend with a record
flu.extend({
  shout: { open: '\u001B[1m', close: '\u001B[22m' },
});
console.log(flu.shout('LOUD'));

TypeScript users can augment the Flu interface in their project to get strong typing for custom styles:

// globals.d.ts (in your app)
declare module 'flu' {
  interface Flu {
    frame: Flu;
    hsl(h: number, s: number, l: number): Flu;
    shout: Flu;
  }
}

Design

• No dependencies; ANSI codes are defined in small constants
• Chainable builder implemented with a Proxy that collects styles
• Nesting is handled by reopening after close codes inside strings
• Extensible registry for styles and dynamic factories

Notes

• Output relies on ANSI escape sequences; ensure your terminal supports them
• Truecolor (rgb/hex) requires a 24-bit color terminal