标签：实现 lock 需要 uniq floor nbsp var 标记 char
全局唯一标识符（GUID，Globally Unique Identifier）也称作 UUID(Universally Unique IDentifier) 。
GUID是一种由算法生成的二进制长度为128位的数字标识符。GUID 的格式为“xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx”，其中的 x 是 0-9 或 a-f 范围内的一个32位十六进制数。在理想情况下，任何计算机和计算机集群都不会生成两个相同的GUID。
GUID 的总数达到了2^128（3.4×10^38）个，所以随机生成两个相同GUID的可能性非常小，但并不为0。GUID一词有时也专指微软对UUID标准的实现。
在生成一些节点的时候需要通过唯一ID来标记，有如下高票答案可供参考
/** Generate a random uuid.** USAGE: Math.uuid(length, radix)* length - the desired number of characters* radix - the number of allowable values for each character.** EXAMPLES:* // No arguments - returns RFC4122, version 4 ID* >>> Math.uuid()* "92329D39-6F5C-4520-ABFC-AAB64544E172"** // One argument - returns ID of the specified length* >>> Math.uuid(15) // 15 character ID (default base=62)* "VcydxgltxrVZSTV"** // Two arguments - returns ID of the specified length, and radix. (Radix must be <= 62)* >>> Math.uuid(8, 2) // 8 character ID (base=2)* "01001010"* >>> Math.uuid(8, 10) // 8 character ID (base=10)* "47473046"* >>> Math.uuid(8, 16) // 8 character ID (base=16)* "098F4D35"*/(function() {// Private array of chars to usevar CHARS = ‘0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz‘.split(‘‘);Math.uuid = function (len, radix) {var chars = CHARS, uuid = [], i;radix = radix || chars.length;if (len) {// Compact formfor (i = 0; i < len; i++) uuid[i] = chars[0 | Math.random()*radix];} else {// rfc4122, version 4 formvar r;// rfc4122 requires these charactersuuid[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. 4.1.5for (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(‘‘);};// A more performant, but slightly bulkier, RFC4122v4 solution. We boost performance// by minimizing calls to random()Math.uuidFast = function() {var chars = CHARS, uuid = new Array(36), rnd=0, r;for (var i = 0; i < 36; i++) {if (i==8 || i==13 || i==18 || i==23) {uuid[i] = ‘-‘;} else if (i==14) {uuid[i] = ‘4‘;} else {if (rnd <= 0x02) rnd = 0x2000000 + (Math.random()*0x1000000)|0;r = rnd & 0xf;rnd = rnd >> 4;uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];}}return uuid.join(‘‘);};// A more compact, but less performant, RFC4122v4 solution:Math.uuidCompact = function() {return ‘xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx‘.replace(/[xy]/g, function(c) {var r = Math.random()*16|0, v = c == ‘x‘ ? r : (r&0x3|0x8);return v.toString(16);});};})();答案下面的评论云：这个方案下的碰撞率不及1/2^^122
另外给大家推荐几种算法
算法2
function guid() {return ‘xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx‘.replace(/[xy]/g, function(c) {var r = Math.random()*16|0, v = c == ‘x‘ ? r : (r&0x3|0x8);return v.toString(16);});}算法3
function guid() {function S4() {return (((1+Math.random())*0x10000)|0).toString(16).substring(1);}return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());}算法4
这个可以指定长度和基数。比如
// 8 character ID (base=2)uuid(8, 2) // "01001010"// 8 character ID (base=10)uuid(8, 10) // "47473046"// 8 character ID (base=16)uuid(8, 16) // "098F4D35"算法5
function uuid() {var s = [];var hexDigits = "0123456789abcdef";for (var i = 0; i < 36; i++) {s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);}s[14] = "4"; // bits 12-15 of the time_hi_and_version field to 0010s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1); // bits 6-7 of the clock_seq_hi_and_reserved to 01s[8] = s[13] = s[18] = s[23] = "-";var uuid = s.join("");return uuid;}当然了，个人还是推荐算法一的，小伙伴们可以根据自己的需求来进行选择。
标签：实现 lock 需要 uniq floor nbsp var 标记 char
原文地址：http://www.cnblogs.com/wangking/p/6032639.html
