getting a string length that contains unicode character exceeding 0xffff

Question

I’m using this character, double sharp \'

Answer 1

String.prototype.codes = function() { return [...this].length };
String.prototype.chars = function() {
    let GraphemeSplitter = require('grapheme-splitter');
    return (new GraphemeSplitter()).countGraphemes(this);
}

console.log("F                                                                    

                                                        
            

Answer 2

Javascript (and Java) strings use UTF-16 encoding.

Unicode codepoint U+0046 (F) is encoded in UTF-16 using 1 codeunit: 0x0046

Unicode codepoint U+1D12A (

Answer 3

That's the function I wrote to get string length in codepoint length

function nbUnicodeLength(string){
    var stringIndex = 0;
    var unicodeIndex = 0;
    var length = string.length;
    var second;
    var first;
    while (stringIndex < length) {

        first = string.charCodeAt(stringIndex);  // returns an integer between 0 and 65535 representing the UTF-16 code unit at the given index.
        if (first >= 0xD800 && first <= 0xDBFF && string.length > stringIndex + 1) {
            second = string.charCodeAt(stringIndex + 1);
            if (second >= 0xDC00 && second <= 0xDFFF) {
                stringIndex += 2;
            } else {
                stringIndex += 1;
            }
        } else {
            stringIndex += 1;
        }

        unicodeIndex += 1;
    }
    return unicodeIndex;
}

Answer 4

To sumarize my comments:

That's just the lenght of that string.

Some chars involve other chars as well, even if it looks like a single character. "̉mủt̉ả̉̉̉t̉ẻd̉W̉ỏ̉r̉̉d̉̉".length == 24

From this (great) blog post, they have a function that will return correct length:

function fancyCount(str){
  const joiner = "\u{200D}";
  const split = str.split(joiner);
  let count = 0;
    
  for(const s of split){
    //removing the variation selectors
    const num = Array.from(s.split(/[\ufe00-\ufe0f]/).join("")).length;
    count += num;
  }
    
  //assuming the joiners are used appropriately
  return count / split.length;
}

console.log(fancyCount("F                                                                    

                                                        
            

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