getSymbols-v2-generator.js

function *getSymbols(s) {
    for (var i = 0; i < s.length - 1; i++) {
        if (s.charCodeAt(i) >> 10 === 0x36 && s.charCodeAt(i + 1) >> 10 === 0x37) {
            yield s.substr(i, 2);
        } else {
            yield s.charAt(i);
        }
    }
    yield s.charAt(i);
}

getSymbols-v2.js

// Just slightly shorter, you know :)

function getSymbols(s) {
    var output = [];
    for (var i = 0; i < s.length - 1; i++) {
        if (s.charCodeAt(i) >> 10 === 0x36 && s.charCodeAt(i + 1) >> 10 === 0x37) {
            output.push(s.substr(i, 2));
        } else {
            output.push(s.charAt(i));
        }
    }
    output.push(s.charAt(i));
    return output;
}

getSymbols.js

function getSymbols(string) {
  var i, output = [];
  for (i = 0; i < string.length - 1; i++) {
    var charCode = string.charCodeAt(i);
    if (charCode >= 0xD800 && charCode <= 0xDBFF) {
      charCode = string.charCodeAt(i + 1);
      if (charCode >= 0xDC00 && charCode <= 0xDFFF) {
        output.push(string.slice(i, i + 2));
        i++;
        continue;
      }
    }
    output.push(string.charAt(i));
  }
  output.push(string.charAt(i));
  return output;
}

For reference, my old version was:

function getSymbols(string) {
  var length = string.length;
  var index = -1;
  var output = [];
  var character;
  var charCode;
  var second;
  while (++index < length) {
    character = string.charAt(index);
    charCode = character.charCodeAt(0);
    if (charCode >= 0xD800 && charCode <= 0xDBFF) {
      second = string.charAt(index + 1);
      if (second >= '\uDC00' && second <= '\uDFFF') {
        ++index;
        output.push(character + second);
      }
      continue;
    }
    output.push(character);
  }
  return output;
}

I’ve updated https://mathiasbynens.be/notes/javascript-unicode#iterating-over-symbols now. Thanks!