二维码解析的坑：为什么slice(-2)截取不到最后两个字符？

const gunCode = scanRes.slice(-2);        // 获取最后2位作为枪编码
const stationCode = scanRes.slice(0, -2); // 前面部分作为站编码
console.log(stationCode, "stationCode", gunCode);

console.log("原始字符串:", JSON.stringify(scanRes));
console.log("字符串长度:", scanRes.length);
console.log("最后两个字符:", JSON.stringify(scanRes.slice(-2)));

// 字符级分析
console.log("字符分析:");
for(let i = 0; i < scanRes.length; i++) {
    const char = scanRes[i];
    console.log(`[${i}]: '${char}' (ASCII: ${char.charCodeAt(0)})`);
}

function parseScanResult(scanRes) {
    // 去除首尾所有空白字符
    const cleanStr = scanRes.trim();
    
    const gunCode = cleanStr.slice(-2);
    const stationCode = cleanStr.slice(0, -2);
    
    console.log("清理后 stationCode:", stationCode, "gunCode:", gunCode);
    return { stationCode, gunCode };
}

function parseScanResultStrict(scanRes) {
    // 只保留数字字符
    const numbersOnly = scanRes.replace(/\D/g, '');
    
    if (numbersOnly.length < 2) {
        throw new Error("有效数字长度不足，无法解析枪编码");
    }
    
    return {
        stationCode: numbersOnly.slice(0, -2),
        gunCode: numbersOnly.slice(-2)
    };
}

function smartParse(scanRes) {
    if (typeof scanRes !== 'string') {
        throw new Error("输入必须为字符串");
    }
    
    // 多重清理
    const cleanStr = scanRes
        .trim()                 // 去除首尾空白
        .replace(/\s+/g, '')    // 去除所有空白字符
        .replace(/\D/g, '');    // 只保留数字
    
    if (cleanStr.length < 2) {
        throw new Error(`清理后字符串长度不足: "${cleanStr}"`);
    }
    
    const result = {
        stationCode: cleanStr.slice(0, -2),
        gunCode: cleanStr.slice(-2)
    };
    
    // 验证结果
    console.log(`解析结果: 站编码=${result.stationCode}, 枪编码=${result.gunCode}`);
    return result;
}

// 使用 JSON.stringify 显示不可见字符
console.log(JSON.stringify(problematicString));

// 字符级调试
function debugString(str) {
    return Array.from(str).map((char, index) => 
        `[${index}]: '${char}' (U+${char.charCodeAt(0).toString(16).padStart(4, '0')})`
    ).join('\n');
}