ansicolor

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

1npm 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:

1require ('colors') // a popular color utility
2
3console.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:

1require ('ansicolor').nice // .nice for unsafe String extensions
2
3console.log (('foo'.cyan + 'bar').red)

Nice!

Crash Course

Importing (as methods):

1import { green, inverse, bgLightCyan, underline, dim } from 'ansicolor'

1const { green, inverse, bgLightCyan, underline, dim } = require ('ansicolor')

Usage:

1console.log ('foo' + green (inverse (bgLightCyan ('bar')) + 'baz') + 'qux')

1console.log (underline.bright.green ('foo' + dim.red.bgLightCyan ('bar'))) // method chaining

Importing (as object):

1import { ansicolor, ParsedSpan } from 'ansicolor' // along with type definitions

1import ansicolor from 'ansicolor'

Nice Mode (not recommended)

1const 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.

1console.log ('foo'.red.bright + 'bar'.bgYellow.underline.dim)

Supported Styles

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

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

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

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

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

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

1const { names } = require ('ansicolor')
2
3names // ['red', 'green', ...

Removing ANSI Styles From Strings

1const { strip } = require ('ansicolor')
2
3strip ('\u001b[0m\u001b[4m\u001b[42m\u001b[31mfoo\u001b[39m\u001b[49m\u001b[24mfoo\u001b[0m')) // 'foofoo'

Checking If Strings Contain ANSI Codes

1const { isEscaped, green } = require ('ansicolor')
2
3isEscaped ('text')         // false
4isEscaped (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.

1const { parse } = require ('ansicolor')
2
3const 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:

1assert.deepEqual (parsed.spans /* or [...parsed] */,
2
3    [ { css: 'font-weight: bold;font-style: italic;background:rgba(255,51,0,1);',
4        italic: true,
5        bold: true,
6        color: { bright: true },
7        bgColor: { name: 'lightRed' },
8        text: 'foo' },
9
10      { css: 'color:rgba(204,0,0,0.5);',
11        color: { name: 'red', dim: true },
12        text: 'bar' } ])

Custom Color Themes

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

1const ansi = require ('ansicolor')
2
3ansi.rgb = {
4
5    black:        [0,     0,   0],    
6    darkGray:     [100, 100, 100],
7    lightGray:    [200, 200, 200],
8    white:        [255, 255, 255],
9
10    red:          [204,   0,   0],
11    lightRed:     [255,  51,   0],
12    
13    green:        [0,   204,   0],
14    lightGreen:   [51,  204,  51],
15    
16    yellow:       [204, 102,   0],
17    lightYellow:  [255, 153,  51],
18    
19    blue:         [0,     0, 255],
20    lightBlue:    [26,  140, 255],
21    
22    magenta:      [204,   0, 204],
23    lightMagenta: [255,   0, 255],
24    
25    cyan:         [0,   153, 255],
26    lightCyan:    [0,   204, 255],
27}

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:

1const { bgGreen, red, parse } = require ('ansicolor')
2
3const string = 'foo' + bgGreen (red.underline.bright.inverse ('bar') + 'baz')
4const parsed = parse (string)
5
6console.log (...parsed.asChromeConsoleLogArguments) // prints with colors in Chrome!

Here's what the format looks like:

1parsed.asChromeConsoleLogArguments // [ "%cfoo%cbar%cbaz",
2                                   //   "",
3                                   //   "font-weight: bold;text-decoration: underline;background:rgba(255,51,0,1);color:rgba(0,204,0,1);",
4                                   //   "background:rgba(0,204,0,1);"
5                                   // ]

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!

Projects That Use ansicolor

• Ololog! — a better console.log for the log-driven debugging junkies
• CCXT — a cryptocurrency trading API with 130+ exchanges
• Grafana — beautiful monitoring & metric analytics & dashboards