node.js - How to count the correct length of a string with emojis in javascript?

Question

I've a little problem.

I'm using NodeJS as backend. Now, an user has a field "biography", where the user can write something about himself.

Suppose that this field has 220 maxlength, and suppose this as input:

?????????????????????????♀??????????????????????♀??????????♀??????????♀??????????♀??????????♀??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? 

As you can see there aren't 220 emojis (there are 37 emojis), but if I do in my nodejs server

console.log(bio.length)

where bio is the input text, I got 221. How could I "parse" the string input to get the correct length? Is it a problem about unicode?

SOLVED

I used this library: https://github.com/orling/grapheme-splitter

I tried that:

var Grapheme = require('grapheme-splitter');
var splitter = new Grapheme();
console.log(splitter.splitGraphemes(bio).length);

and the length is 37. It works very well!

Answer 1

1. str.length gives the count of UTF-16 units.

2. Unicode-proof way to get string length in codepoints (in characters) is [...str].length as iterable protocol splits the string to codepoints.

3. If we need the length in graphemes (grapheme clusters), we have these native ways:

   a. Unicode property escapes in RegExp. See for example: Unicode-aware version of w or Matching emoji.

   b. Intl.Segmenter — coming soon, probably in ES2021. Can be tested with a flag in the last V8 versions (realization was synced with the last spec in V8 86). Unflagged (shipped) in V8 87.

See also:

• The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)

• What every JavaScript developer should know about Unicode

• JavaScript has a Unicode problem

• Unicode-aware regular expressions in ES2015

• ES6 Strings (and Unicode, ?) in Depth

• JavaScript for impatient programmers. Unicode – a brief introduction