printable-characters

A little helper for handling strings containing zero width characters, ANSI styling, whitespaces, newlines, weird Unicode 💩 symbols, etc.

Determining the real (visible) length of a string

const { strlen } = require ('printable-characters')
 
strlen ('foo bar') // === 7
strlen ('\u001b[106mfoo bar\u001b[49m') // === 7

Detecting blank text

const { isBlank } = require ('printable-characters')
 
isBlank ('foobar') // === false
isBlank ('\u001b[106m  \t  \t   \n     \u001b[49m') // === true

Obtaining a blank string of the same width

const { blank } = require ('printable-characters')
 
blank ('💩')          // === ' '
blank ('foo')         // === '   '
blank ('\tfoo \nfoo') // === '\t    \n   '
blank ('\u001b[22m\u001b[1mfoo \t\u001b[39m\u001b[22m')) // === '    \t'

Matching invisible characters

const { ansiEscapeCodes, zeroWidthCharacters } = require ('printable-characters')
 
const s = '\u001b[106m' + 'foo' + '\n' + 'bar' + '\u001b[49m'
 
s.replace (ansiEscapeCodes, '')     // === 'foo\nbar'
 .replace (zeroWidthCharacters, '') // === 'foobar'

Getting the first N visible symbols, preserving the invisible parts

Use for safely truncating strings to maximum width without breaking ANSI codes:

const { first } = require ('printable-characters')
 
const s = '\u001b[22mfoobar\u001b[22m'
 
first (s, 0) // === '\u001b[22m\u001b[22m'
first (s, 1) // === '\u001b[22mf\u001b[22m'
first (s, 3) // === '\u001b[22mfoo\u001b[22m'
first (s, 6) // === '\u001b[22mfoobar\u001b[22m'

Extracting the invisible parts followed by the visible ones (parsing)

const { partition } = require ('printable-characters')
 
partition ('')                        // [                                                     ])
partition ('foo')                     // [['',          'foo']                                 ])
partition ('\u001b[1mfoo')            // [['\u001b[1m', 'foo']                                 ])
partition ('\u001b[1mfoo\u0000bar')   // [['\u001b[1m', 'foo'],   ['\u0000', 'bar']            ])
partition ('\u001b[1mfoo\u0000bar\n') // [['\u001b[1m', 'foo'],   ['\u0000', 'bar'], ['\n', '']])

Applications

• as-table — a simple function that prints objects as ASCII tables
• string.bullet — ASCII-mode bulleting for the list-style data
• string.ify — a fancy pretty printer for the JavaScript entities
• Ololog! — a better console.log for the log-driven debugging junkies!

TODO

Handle multi-component emojis, as in this article:

assert.equal (strlen ('👩‍❤️‍💋‍👩'), 1)  // FAILING, see http://blog.jonnew.com/posts/poo-dot-length-equals-two for possible solution
assert.equal (blank ('👩‍❤️‍💋‍👩'), ' ') // FAILING, see http://blog.jonnew.com/posts/poo-dot-length-equals-two for possible solution