// 笛卡尔乘积函数
    const dicar = (arr) => arr
        .reduce((acc, cur) => acc.length === 0
                ? cur
                : acc
                    // 乘积
                    .map(x => cur.map(y => x + '-' + y))
                    // 拍平
                    .reduce((acc, cur) => acc.concat(cur), []),
            []
        )
        .join(',')