How JavaScript generates a globally unique identifier (GUID,UUID) _javascript tips

A globally unique identifier (guid,globally unique Identifier) is also known as a UUID (universally unique Identifier).

A GUID is a 128-bit numeric identifier generated by the algorithm in binary length. The GUID is formatted as "Xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", where X is a 32-bit hexadecimal number in the range 0-9 or a-f. Ideally, no computer or cluster of computers will generate two identical GUIDs.

The total number of GUIDs reached 2^128 (3.4x10^38), so the probability of randomly generating two identical GUIDs is very small, but not 0. The term GUID sometimes refers to Microsoft's implementation of the UUID standard.

In the generation of some nodes need to be marked by a unique ID, with the following high vote answer for reference

function Generateuuid () {
var d = new Date (). GetTime ();
var uuid = ' xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx '. Replace (/[xy]/g, function (c) {
  var r = (d + math.random () *16)%16 | 0 ;
  D = Math.floor (D/16);
  Return (c== ' x ' r: (r&0x3|0x8)). ToString (
); return uuid;
};

The answer to the following comment cloud: The collision rate under this scheme is less than 1/2^^122

In addition to recommend several algorithms

Algorithm 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;
  }

 

Algorithm 3

function guid () {
  function S4 () {return ((
    1+math.random ()) *0x10000) |). toString. substring (1);
  }
  Return (S4 () +s4 () + "-" +s4 () + "-" +s4 () + "-" +s4 () + "-" +S4 () +s4 () +s4 ());
}
 

Algorithm 4

function uuid (len, radix) {
  var chars = ' 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz '. Split (' ');
  var 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 < i++) {
    if (!uuid[i]) {
     R = 0 | Math.random () *16;
     Uuid[i] = chars[(i = = 19)? (R & 0x3) | 0X8:R];
 
  }} Return Uuid.join (");
}

This can specify the length and cardinality. Like what

8 character ID (base=2)
uuid (8, 2)//"01001010"
//8 character ID (base=10)
uuid (8, ten)//"47473046"
8 character ID (base=16)
uuid (8)//"098f4d35"

Algorithm 5

function uuid () {
  var s = [];
  var hexdigits = "0123456789abcdef";
  for (var i = 0; i < 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
  s[8] = s[13] = s[18] = s[23] = "-";
 
  var uuid = S.join ("");
  return uuid;
}
 

Of course, the individual or recommended algorithm one, the small partners can according to their own needs to choose.