grapheme-splitter

by orling

A JavaScript library that breaks strings into their individual user-perceived characters.

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Background

In JavaScript there is not always a one-to-one relationship between string characters and what a user would call a separate visual "letter". Some symbols are represented by several characters. This can cause issues when splitting strings and inadvertently cutting a multi-char letter in half, or when you need the actual number of letters in a string.

For example, emoji characters like "🌷","🎁","💩","😜" and "👍" are represented by two JavaScript characters each (high surrogate and low surrogate). That is,

"🌷".length == 2

The combined emoji are even longer:

javascript
"🏳️‍🌈".length == 6

What's more, some languages often include combining marks - characters that are used to modify the letters before them. Common examples are the German letter ü and the Spanish letter ñ. Sometimes they can be represented alternatively both as a single character and as a letter + combining mark, with both forms equally valid:

var two = "ñ"; // unnormalized two-char n+◌̃  , i.e. "\u006E\u0303";
var one = "ñ"; // normalized single-char, i.e. "\u00F1"
console.log(one!=two); // prints 'true'

Unicode normalization, as performed by the popular punycode.js library or ECMAScript 6's String.normalize, can sometimes fix those differences and turn two-char sequences into single characters. But it is not enough in all cases. Some languages like Hindi make extensive use of combining marks on their letters, that have no dedicated single-codepoint Unicode sequences, due to the sheer number of possible combinations. For example, the Hindi word "अनुच्छेद" is comprised of 5 letters and 3 combining marks:

अ + न + ु + च + ् + छ + े + द

which is in fact just 5 user-perceived letters:

अ + नु + च् + छे + द

and which Unicode normalization would not combine properly. There are also the unusual letter+combining mark combinations which have no dedicated Unicode codepoint. The string Z͑ͫ̓ͪ̂ͫ̽͏̴̙̤̞͉͚̯̞̠͍A̴̵̜̰͔ͫ͗͢L̠ͨͧͩ͘G̴̻͈͍͔̹̑͗̎̅͛́Ǫ̵̹̻̝̳͂̌̌͘ obviously has 5 separate letters, but is in fact comprised of 58 JavaScript characters, most of which are combining marks.

Enter the grapheme-splitter.js library. It can be used to properly split JavaScript strings into what a human user would call separate letters (or "extended grapheme clusters" in Unicode terminology), no matter what their internal representation is. It is an implementation on the Default Grapheme Cluster Boundary of UAX #29.

Installation

You can use the index.js file directly as-is. Or you you can install

grapheme-splitter
to your project using the NPM command below:
$ npm install --save grapheme-splitter

Tests

To run the tests on

grapheme-splitter
, use the command below:
$ npm test

Usage

Just initialize and use:

var splitter = new GraphemeSplitter();

// split the string to an array of grapheme clusters (one string each) var graphemes = splitter.splitGraphemes(string);

// iterate the string to an iterable iterator of grapheme clusters (one string each) var graphemes = splitter.iterateGraphemes(string);

// or do this if you just need their number var graphemeCount = splitter.countGraphemes(string);

Examples

var splitter = new GraphemeSplitter();

// plain latin alphabet - nothing spectacular splitter.splitGraphemes("abcd"); // returns ["a", "b", "c", "d"]

// two-char emojis and six-char combined emoji splitter.splitGraphemes("🌷🎁💩😜👍🏳️‍🌈"); // returns ["🌷","🎁","💩","😜","👍","🏳️‍🌈"]

// diacritics as combining marks, 10 JavaScript chars splitter.splitGraphemes("Ĺo͂řȩm̅"); // returns ["Ĺ","o͂","ř","ȩ","m̅"]

// individual Korean characters (Jamo), 4 JavaScript chars splitter.splitGraphemes("뎌쉐"); // returns ["뎌","쉐"]

// Hindi text with combining marks, 8 JavaScript chars splitter.splitGraphemes("अनुच्छेद"); // returns ["अ","नु","च्","छे","द"]

// demonic multiple combining marks, 75 JavaScript chars splitter.splitGraphemes("Z͑ͫ̓ͪ̂ͫ̽͏̴̙̤̞͉͚̯̞̠͍A̴̵̜̰͔ͫ͗͢L̠ͨͧͩ͘G̴̻͈͍͔̹̑͗̎̅͛́Ǫ̵̹̻̝̳͂̌̌͘!͖̬̰̙̗̿̋ͥͥ̂ͣ̐́́͜͞"); // returns ["Z͑ͫ̓ͪ̂ͫ̽͏̴̙̤̞͉͚̯̞̠͍","A̴̵̜̰͔ͫ͗͢","L̠ͨͧͩ͘","G̴̻͈͍͔̹̑͗̎̅͛́","Ǫ̵̹̻̝̳͂̌̌͘","!͖̬̰̙̗̿̋ͥͥ̂ͣ̐́́͜͞"]

TypeScript

Grapheme splitter includes TypeScript declarations.

import GraphemeSplitter = require('grapheme-splitter')

const splitter = new GraphemeSplitter()

const split: string[] = splitter.splitGraphemes('Z͑ͫ̓ͪ̂ͫ̽͏̴̙̤̞͉͚̯̞̠͍A̴̵̜̰͔ͫ͗͢L̠ͨͧͩ͘G̴̻͈͍͔̹̑͗̎̅͛́Ǫ̵̹̻̝̳͂̌̌͘!͖̬̰̙̗̿̋ͥͥ̂ͣ̐́́͜͞')

Acknowledgements

This library is heavily influenced by Devon Govett's excellent grapheme-breaker CoffeeScript library at https://github.com/devongovett/grapheme-breaker with an emphasis on ease of integration and pure JavaScript implementation.

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