全局唯一標識符（GUID，Globally Unique Identifier）也稱作 UUID(Universally Unique IDentifier) 。
GUID是一種由算法生成的二進制長度為128位的數字標識符。GUID 的格式為“xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx”，其中的 x 是 0-9 或 a-f 范圍內的一個32位十六進制數。在理想情況下，任何計算機和計算機集群都不會生成兩個相同的GUID。
GUID 的總數達到了2^128（3.4×10^38）個，所以隨機生成兩個相同GUID的可能性非常小，但並不為0。GUID一詞有時也專指微軟對UUID標准的實現。
在生成一些節點的時候需要通過唯一ID來標記，有如下高票答案可供參考
/*
* 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 use
var
CHARS =
'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
.split(
''
);
Math.uuid =
function
(len, radix) {
var
chars = CHARS, uuid = [], i;
radix = radix || chars.length;
if
(len) {
// Compact form
for
(i = 0; i < len; 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(
''
);
};
// 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);
});
};
})();
另外還有幾種寫法：
答案下面的評論雲：這個方案下的碰撞率不及1/2^^122
另外給大家推薦幾種算法
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
這個可以指定長度和基數。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 0010
s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1);
// bits 6-7 of the clock_seq_hi_and_reserved to 01
s[8] = s[13] = s[18] = s[23] =
"-"
;
var
uuid = s.join(
""
);
return
uuid;
}
當然了，個人還是推薦算法一的，小伙伴們可以根據自己的需求來進行選擇。