ansicolor

A JavaScript ANSI color/style management. ANSI parsing. ANSI to CSS. Small, clean, no dependencies.

npm install ansicolor

What For

String coloring with ANSI escape codes
Solves the style hierarchy problem (when other similar tools fail)
Parsing/removing ANSI style data from strings
Converting ANSI styles to CSS or a Chrome DevTools-compatible output
A middleware for your platform-agnostic logging system

Why Another One?

Other tools lack consistency, failing to solve a simple hierarchy problem:

require ('colors') // a popular color utility

console.log (('foo'.cyan + 'bar').red)

WTF?! The bar word above should be rendered in red, but it's not! That sucks. It's because ANSI codes are linear, not hierarchical (as with XML/HTML). A special kind of magic is needed to make this work. Ansicolor does that magic for you:

require ('ansicolor').nice // .nice for unsafe String extensions

console.log (('foo'.cyan + 'bar').red)

Nice!

Crash Course

Importing (as methods):

import { green, inverse, bgLightCyan, underline, dim } from 'ansicolor'

const { green, inverse, bgLightCyan, underline, dim } = require ('ansicolor')

Usage:

console.log ('foo' + green (inverse (bgLightCyan ('bar')) + 'baz') + 'qux')

console.log (underline.bright.green ('foo' + dim.red.bgLightCyan ('bar'))) // method chaining

Importing (as object):

import { ansicolor, ParsedSpan } from 'ansicolor' // along with type definitions

import ansicolor from 'ansicolor'

Nice Mode (not recommended)

const ansi = require ('ansicolor').nice

The ('ansicolor').nice export defines styling APIs on the String prototype directly. It uses an ad-hoc DSL (sort of) for infix-style string coloring. The nice is convenient, but not safe, avoid using it in public modules, as it alters global objects, and that might cause potential hard-to-debug compatibility issues.

console.log ('foo'.red.bright + 'bar'.bgYellow.underline.dim)

Supported Styles

'foreground colors'
    .red.green.yellow.blue.magenta.cyan.white.darkGray.black

'light foreground colors'
    .lightRed.lightGreen.lightYellow.lightBlue.lightMagenta.lightCyan.lightGray

'background colors'
    .bgRed.bgGreen.bgYellow.bgBlue.bgMagenta.bgCyan.bgWhite.bgDarkGray.bgBlack

'light background colors'
    .bgLightRed.bgLightGreen.bgLightYellow.bgLightBlue.bgLightMagenta.bgLightCyan.bgLightGray

'styles'
    .bright.dim.italic.underline.inverse // your platform should support italic

You also can obtain all those style names (for reflection purposes):

const { names } = require ('ansicolor')

names // ['red', 'green', ...

Removing ANSI Styles From Strings

const { strip } = require ('ansicolor')

strip ('\u001b[0m\u001b[4m\u001b[42m\u001b[31mfoo\u001b[39m\u001b[49m\u001b[24mfoo\u001b[0m')) // 'foofoo'

Checking If Strings Contain ANSI Codes

const { isEscaped, green } = require ('ansicolor')

isEscaped ('text')         // false
isEscaped (green ('text')) // true

Converting to CSS/HTML

Inspection of ANSI styles in arbitrary strings is essential when implementing platform-agnostic logging — that piece of code is available under command line interface and in a browser as well. Here's an example of how you would parse a colored string into an array-like structure. That structure can be traversed later to build HTML/JSON/XML or any other markup/syntax.

const { parse } = require ('ansicolor')

const parsed = parse ('foo'.bgLightRed.bright.italic + 'bar'.red.dim)

The ansi.parse () method will return a pseudo-array of styled spans, you can iterate over it with a for ... of loop and convert it to an array with the spread operator (...). Also, there's the .spans property for obtaining the already-spread array directly:

assert.deepEqual (parsed.spans /* or [...parsed] */,

    [ { css: 'font-weight: bold;font-style: italic;background:rgba(255,51,0,1);',
        italic: true,
        bold: true,
        color: { bright: true },
        bgColor: { name: 'lightRed' },
        text: 'foo' },

      { css: 'color:rgba(204,0,0,0.5);',
        color: { name: 'red', dim: true },
        text: 'bar' } ])

Custom Color Themes

You can change default RGB values (won't work in terminals, affects only the ANSI→CSS transformation part):

const ansi = require ('ansicolor')

ansi.rgb = {

    black:        [0,     0,   0],    
    darkGray:     [100, 100, 100],
    lightGray:    [200, 200, 200],
    white:        [255, 255, 255],

    red:          [204,   0,   0],
    lightRed:     [255,  51,   0],
    
    green:        [0,   204,   0],
    lightGreen:   [51,  204,  51],
    
    yellow:       [204, 102,   0],
    lightYellow:  [255, 153,  51],
    
    blue:         [0,     0, 255],
    lightBlue:    [26,  140, 255],
    
    magenta:      [204,   0, 204],
    lightMagenta: [255,   0, 255],
    
    cyan:         [0,   153, 255],
    lightCyan:    [0,   204, 255],
}

Chrome DevTools Compatibility

Web browsers usually implement their own proprietary CSS-based color formats for console.log and most of them fail to display standard ANSI colors. Ansicolor offers you a helper method to convert ANSI-styled strings to browser-compatible argument lists acceptable by Chrome's console.log:

const { bgGreen, red, parse } = require ('ansicolor')

const string = 'foo' + bgGreen (red.underline.bright.inverse ('bar') + 'baz')
const parsed = parse (string)

console.log (...parsed.asChromeConsoleLogArguments) // prints with colors in Chrome!

Here's what the format looks like:

parsed.asChromeConsoleLogArguments // [ "%cfoo%cbar%cbaz",
                                   //   "",
                                   //   "font-weight: bold;text-decoration: underline;background:rgba(255,51,0,1);color:rgba(0,204,0,1);",
                                   //   "background:rgba(0,204,0,1);"
                                   // ]

Play with this feature online: demo page. Open the DevTools console and type expressions in the input box to see colored console output.

Happy logging!