kubernetes-handbook/chalk

Terminal string styling done right

colors.js used to be the most popular string styling module, but it has serious deficiencies like extending String.prototype which causes all kinds of problems. Although there are other ones, they either do too much or not enough.

Chalk is a clean and focused alternative.

Why

• Highly performant
• Doesn't extend String.prototype
• Expressive API
• Ability to nest styles
• Clean and focused
• Auto-detects color support
• Actively maintained
• Used by ~4500 modules as of July 15, 2015

Install

$ npm install --save chalk

Usage

Chalk comes with an easy to use composable API where you just chain and nest the styles you want.

var chalk = require('chalk');

// style a string
chalk.blue('Hello world!');

// combine styled and normal strings
chalk.blue('Hello') + 'World' + chalk.red('!');

// compose multiple styles using the chainable API
chalk.blue.bgRed.bold('Hello world!');

// pass in multiple arguments
chalk.blue('Hello', 'World!', 'Foo', 'bar', 'biz', 'baz');

// nest styles
chalk.red('Hello', chalk.underline.bgBlue('world') + '!');

// nest styles of the same type even (color, underline, background)
chalk.green(
	'I am a green line ' +
	chalk.blue.underline.bold('with a blue substring') +
	' that becomes green again!'
);

Easily define your own themes.

var chalk = require('chalk');
var error = chalk.bold.red;
console.log(error('Error!'));

Take advantage of console.log string substitution.

var name = 'Sindre';
console.log(chalk.green('Hello %s'), name);
//=> Hello Sindre

API

chalk.<style>[.<style>...](string, [string...])

Example: chalk.red.bold.underline('Hello', 'world');

Chain styles and call the last one as a method with a string argument. Order doesn't matter, and later styles take precedent in case of a conflict. This simply means that Chalk.red.yellow.green is equivalent to Chalk.green.

Multiple arguments will be separated by space.

chalk.enabled

Color support is automatically detected, but you can override it by setting the enabled property. You should however only do this in your own code as it applies globally to all chalk consumers.

If you need to change this in a reusable module create a new instance:

var ctx = new chalk.constructor({enabled: false});

chalk.supportsColor

Detect whether the terminal supports color. Used internally and handled for you, but exposed for convenience.

Can be overridden by the user with the flags --color and --no-color. For situations where using --color is not possible, add an environment variable FORCE_COLOR with any value to force color. Trumps --no-color.

chalk.styles

Exposes the styles as ANSI escape codes.

Generally not useful, but you might need just the .open or .close escape code if you're mixing externally styled strings with your own.

var chalk = require('chalk');

console.log(chalk.styles.red);
//=> {open: '\u001b[31m', close: '\u001b[39m'}

console.log(chalk.styles.red.open + 'Hello' + chalk.styles.red.close);

chalk.hasColor(string)

Check whether a string has color.

chalk.stripColor(string)

Strip color from a string.

Can be useful in combination with .supportsColor to strip color on externally styled text when it's not supported.

Example:

var chalk = require('chalk');
var styledString = getText();

if (!chalk.supportsColor) {
	styledString = chalk.stripColor(styledString);
}

Styles

Modifiers

• reset
• bold
• dim
• italic (not widely supported)
• underline
• inverse
• hidden
• strikethrough (not widely supported)

Colors

• black
• red
• green
• yellow
• blue (on Windows the bright version is used as normal blue is illegible)
• magenta
• cyan
• white
• gray

Background colors

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

256-colors

Chalk does not support anything other than the base eight colors, which guarantees it will work on all terminals and systems. Some terminals, specifically xterm compliant ones, will support the full range of 8-bit colors. For this the lower level ansi-256-colors package can be used.

Windows

If you're on Windows, do yourself a favor and use cmder instead of cmd.exe.

Related

• chalk-cli - CLI for this module
• ansi-styles - ANSI escape codes for styling strings in the terminal
• supports-color - Detect whether a terminal supports color
• strip-ansi - Strip ANSI escape codes
• has-ansi - Check if a string has ANSI escape codes
• ansi-regex - Regular expression for matching ANSI escape codes
• wrap-ansi - Wordwrap a string with ANSI escape codes

License

MIT © Sindre Sorhus