uuid 添加时间戳防止uuid重复

// 生成uuid 方法
function uuid2(len=30, radix) {
var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'.split('');
var timestamp = new Date().getTime(); // 获取当前时间戳 以防止 uuid 重复生成
var uuid = [],
i;
radix = radix || chars.length;
if (len) {
// Compact form
for (i = 0; i < len - String(timestamp).length; i++) {
uuid[i] = chars[0 | Math.random() * radix];
}
} else {
// rfc4122, version 4 form
var r;

	// rfc4122 requires these characters
	uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
	uuid[14] = '4';

	// Fill in random data.  At i==19 set the high bits of clock sequence as
	// per rfc4122, sec. 4.1.5
	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('') + timestamp;

}