js代码

var alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_".split(""),
                length = 64,
                map = {},
                seed = 0,
                i = 0,
                prev;

        function encode(num) {
            var encoded = "";
            do {
                encoded = alphabet[num % length] + encoded;
                num = Math.floor(num / length)
            } while (num > 0);
            return encoded
        }

        function yeast() {
            var now = encode(+new Date);
            if (now !== prev) return seed = 0, prev = now;
            return now + "." + encode(seed++)
        }
        aaa =yeast();