kleur

What is kleur?

The kleur npm package is a library for formatting terminal text with ANSI colors. It provides a simple and chainable API to style strings that are output to the console with various colors, backgrounds, and text styles.

What are kleur's main functionalities?

Coloring text

This feature allows you to apply text color to your console output. The example shows how to color the text green.

const kleur = require('kleur');
console.log(kleur.green('Hello world!'));

Chaining styles

Kleur supports chaining multiple styles together. In this example, the text 'Error!' is styled to be red, bold, and underlined.

const kleur = require('kleur');
console.log(kleur.red().bold().underline('Error!'));

Background colors

You can also set background colors for your text. Here, the text 'Info' has a blue background with white foreground color.

const kleur = require('kleur');
console.log(kleur.bgBlue().white('Info'));

Conditional styling

Kleur allows conditional styling, where you can enable or disable colors based on certain conditions. In this example, the red color is applied only if the environment is not production.

const kleur = require('kleur');
const enabled = process.env.NODE_ENV !== 'production';
console.log(kleur.enabled(enabled).red('Only styled if not in production'));

Other packages similar to kleur

chalk

Chalk is a popular npm package similar to kleur that allows for styling terminal strings. It offers a more extensive API and additional features like template literal support and custom themes, but it is slightly larger in size compared to kleur.

colors

Colors is another package that provides ANSI color formatting for text in the terminal. It extends String.prototype to add color properties, which some developers may find less clean than the functional approach taken by kleur.

ansi-colors

Ansi-colors is a lightweight package that focuses on performance. Like kleur, it does not extend String.prototype and has a chainable API, but it has fewer dependencies and is designed to be as minimal as possible.

README

The fastest Node.js library for formatting terminal text with ANSI colors~!

Features

• No dependencies
• Super lightweight & performant
• Supports nested & chained colors
• No String.prototype modifications
• Supports printf formatting
• Conditional color support
• Familiar API

Heavily inspired by ansi-colors. See Credits for more info!

Install

$ npm install --save kleur

Usage

const kleur = require('kleur');

// basic usage
kleur.red('red text');

// or variadic arguments
kleur.red('this', 'is', 'also', 'red');

// or printf formatting
kleur.red('%s, %s!', 'hello', 'world');

// chained methods
kleur.blue.bold.underline('howdy partner');

// nested methods
kleur.bold(`${ kleur.bgRed.white('[ERROR]') } ${ kleur.red.italic('Something happened')}`);

Chained Methods

console.log(kleur.bold.red('this is a bold red message'));
console.log(kleur.bold.italic('this is a bold italicized message'));
console.log(kleur.bold.yellow.bgRed.italic('this is a bold yellow italicized message'));
console.log(kleur.green.bold.underline('this is a bold green underlined message'));

Nested Methods

const { yellow, red, cyan } = require('kleur');

// with template literals
console.log(yellow(`foo ${red.bold('red')} bar ${cyan('cyan')} baz`));

// or variadic arguments
console.log(yellow('foo', red.bold('red'), 'bar', cyan('cyan'), 'baz'));

printf Formatting

See util.format for documentation

const { yellow, bgGreen, bold } = require('kleur');

// basic usage
console.log(bold.cyan('%s, %s!', 'Hello', 'World', '-Anonymous'));

// or with nested colors
console.log( bold('%s-like %s... %s!', 'printf', bgGreen.black('formatting'), yellow('YAY')) );

Clear Formatting

Manually strip all ANSI codes from a given string.

let str = kleur.blue('Howdy partner');
//=> styled

kleur.clear(str);
//=> 'Howdy partner'

Conditional Support

Toggle color support as needed; kleur assumes it's always enabled.

const kleur = require('kleur');

// manually disable
kleur.enabled = false;

// or use a library to detect support
kleur.enabled = require('color-support').level;

console.log(kleur.red('I will only be colored red if the terminal supports colors'));

API

Any kleur method returns a String (when invoked, not chained). It's up to the developer to pass the output to destinations like console.log, process.stdout.write, etc.

The methods below are grouped by type for legibility purposes only. They each can be chained or nested with one another.

Colors:

black — red — green — yellow — blue — magenta — cyan — white — gray

Backgrounds:

bgBlack — bgRed — bgGreen — bgYellow — bgBlue — bgMagenta — bgCyan — bgWhite

Modifiers:

reset — bold — dim — italic* — underline — inverse — hidden — strikethrough*

^{* Not widely supported}

Benchmarks

Using Node v8.9.0

Load time

ansi-colors: 1.150ms
chalk: 8.440ms
clorox: 0.471ms
kleur: 0.611ms

Performance

# All Colors
  ansi-colors x 60,646 ops/sec ±0.49% (96 runs sampled)
  chalk x 7,228 ops/sec ±3.25% (73 runs sampled)
  clorox x 86,631 ops/sec ±0.59% (94 runs sampled)
  kleur x 95,595 ops/sec ±0.24% (96 runs sampled)

# Stacked colors
  ansi-colors x 13,576 ops/sec ±0.42% (93 runs sampled)
  chalk x 1,669 ops/sec ±4.56% (71 runs sampled)
  clorox x 26,166 ops/sec ±1.44% (91 runs sampled)
  kleur x 28,674 ops/sec ±0.29% (93 runs sampled)

# Nested colors
  ansi-colors x 28,712 ops/sec ±0.60% (96 runs sampled)
  chalk x 3,446 ops/sec ±4.59% (69 runs sampled)
  Clorox x 40,821 ops/sec ±1.90% (94 runs sampled)
  kleur x 43,242 ops/sec ±0.17% (97 runs sampled)

Credits

This project is based on Brian Woodward's awesome ansi-colors project. My original implementation involved writing into a global state — first by writing into an output string, and then by saving the keys array into the $ directly. Both approaches were leaky & allowed for accidental chains/overwrites. In turn, I borrowed ansi-colors's approach in writing keys state into each chain directly.

Aside from the performance boost, kleur exists as a separate module because I've removed some of ansi-colors's defining features, like bright color variants and symbols. It's tailor-made for my needs and experimentation.

You'll probably want to use ansi-colors, especially if you need any of those features! You'll be in good company!

The benchmark suite is also imported directly from ansi-colors :raised_hands:

License

MIT © Luke Edwards