js随机序列生成

/*
    @param len {number} 长度
    @param radix {number} 基数
*/

function uuid(len, radix) {
    let chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');
    let uuid = [],
        i;
    radix = radix || chars.length;
 
    if (len) {
        for (i = 0; i < len; i++) uuid[i] = chars[0 | Math.random() * radix];
    } else {
        let r;
        uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
        uuid[14] = '4';
        for (i = 0; i < 36; i++) {
            if (!uuid[i]) {
                r = 0 | Math.random() * 16;
                uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
            }
        }
    }
 
    return uuid.join('');
}