The 140-Character Lie — JavaScript Bug Hunt

Briefing

Inspired by Twitter's infamous character-counter quirks: links are supposed to cost a flat 23 characters (the t.co wrapper), and an emoji is one character to a human — yet the composer keeps blocking tweets that should fit.

Fix charCount.js so the counter matches the spec.

Bug report

BUG-140 · Reported by: composer team

Spec: every URL counts as exactly 23 characters; everything else counts in user-perceived characters (code points), not UTF-16 units.

Observed:

• "check https://a.very/long/path…" is counted at the URL's full length
• a single 🙂 is counted as TWO characters

Logs

[composer] countTweet("🙂") -> 2 (expected 1)
[composer] over-limit block fired at 138 visible chars

The code as shipped

src/tweet/charCount.js (editable)

// Counts a tweet the way the platform bills it.
// Spec: URLs cost a flat 23 characters; text is counted in code points.
var URL_COST = 23;

exports.countTweet = function (text) {
  return text.length;
};