博客

emoji的Unicode类型非常多，难以一条规则通吃，弄了半天，暂时就说结论：

findSurrogatePair('3420e3') // 4️⃣
function findSurrogatePair (point) {
    let pointX16 = parseInt(point, 16)

    if (pointX16 <= 0xffff) {
        return String.fromCodePoint(pointX16)
    } else if (0xffff < pointX16 && pointX16 <= 0xfffff) {
        // https://segmentfault.com/a/1190000009560472
        let offset = pointX16 - 0x10000
        let lead = 0xd800 + (offset >> 10)
        let trail = 0xdc00 + (offset & 0x3ff)
        return String.fromCodePoint(lead, trail)
    } else if (0xfffff < pointX16 && pointX16 <= 0xffffff) {
        let start = pointX16 >> 16
        let end = pointX16 & 0xffff
        return String.fromCodePoint(start, 0xFE0F, end)
    } else if (0x0fffffffff < pointX16 && pointX16 < 0xffffffffff) {
        let start = parseInt(point.slice(0, 5), 16)
        let end = parseInt(point.slice(5, 10), 16)
        return String.fromCodePoint(start, end)
    } else {
        console.error('unfind emoji code: ' + point)
        return point
    }
}

还有其他长度的emoji还待研究补充，有空把原理都补全