Emoji Cheat Sheet

Practical Snippet

Key points: (1) U+FE0F makes visually identical emoji strictly unequal, so strip it or always append it before storage, otherwise dedup and cache keys diverge; (2) flags can only be built from two-letter alpha-2 — convert alpha-3 or numeric codes first, and Windows may render two letters due to a missing font rather than an encoding error; (3) any length limit must state whether it counts UTF-16 code units, code points or UTF-8 bytes; (4) status icons in real UI should use cross-platform-stable symbols like ✔⚠✖ instead of relying on an emoji font.

// ① 变体选择符 U+FE0F：肉眼相同但不相等
const a = '❤️'   // ❤️ 带变体选择符
const b = '❤'         // ❤ 不带
console.log(a === b)                 // false  ← 坑
console.log(a.normalize('NFC') === b.normalize('NFC'))  // 仍 false（FE0F 不被 NFC 去除）

// 规范化：入库/比较前统一去掉 U+FE0F
const stripVS = s => s.replace(/️/g, '')
console.log(stripVS(a) === b)         // true  ✅

// ② 旗帜只能由 alpha-2 生成
const flagOf = (alpha2) => {
  if (alpha2.length !== 2) throw new Error('need alpha-2')
  const base = 0x1f1e6                       // 'A' 的 regional indicator
  return String.fromCodePoint(
    base + (alpha2.toUpperCase().charCodeAt(0) - 65),
    base + (alpha2.toUpperCase().charCodeAt(1) - 65),
  )
}
console.log(flagOf('cn'), flagOf('de'))      // 🇨🇳 🇩🇪

// ③ 量一下「字符数 vs 码点数 vs 字节数」
const s = 'a中🛠️'
console.log(s.length)                         // 4  UTF-16 计数单位
console.log([...s].length)                    // 3  码点数
console.log(new TextEncoder().encode(s).length)  // 8  UTF-8 字节数
// ⚠️ 限制字符串长度时必须明确用哪一种口径

// ④ 稳定 UI 图标：别依赖 emoji 字体
const ICON = { ok: '\\u2714', warn: '\\u26A0', err: '\\u2716' }  // ✔ ⚠ ✖
console.log(ICON.ok, ICON.warn, ICON.err)     // 跨平台呈现更一致