获取包含超过0xffff的Unicode字符的字符串长度

"̉mủt̉ả̉̉̉t̉ẻd̉W̉ỏ̉r̉̉d̉̉".length == 24

this (great) blog post

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𝄪") == 2) // true

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

console.log("F𝄪".codes());     // 2
console.log("👩‍❤️‍💋‍👩".codes());     // 8
console.log("❤️".codes());      // 2

console.log("F𝄪".chars());     // 2
console.log("👩‍❤️‍💋‍👩".chars());     // 1
console.log("❤️".chars());      // 1

F 0x0046

𝄪 0xD834 0xDD2A

length 计算编码的代码单元数,而不是Unicode代码点数。