提取文件后缀名，生成随机字符串

生成随机字符串

function random_string(len) {len = len || 32;var chars = 'ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678';var maxPos = chars.length;var pwd = '';for (i = 0; i < len; i++) {pwd += chars.charAt(Math.floor(Math.random() * maxPos));}return pwd;}

function get_suffix(filename) {pos = filename.lastIndexOf('.')suffix = ''if (pos != -1) {suffix = filename.substring(pos)}return suffix;}