Four ways to generate UUID for JS

The globally unique identifier (guid,globally unique Identifier) is also known as the UUID (universally unique Identifier).

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

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

Method One

functionuuid() {

     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; }Method Two 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);      }); }Method Three function guid() {      function S4() {         return (((1+Math.random())*0x10000)|0).toString(16).substring(1);      }      return (S4()+S4()+ "-" +S4()+ "-" +S4()+ "-" +S4()+ "-" +S4()+S4()+S4()); }Method Four 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 < 36; i++) {          if (!uuid[i]) {            r = 0 | Math.random()*16;            uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];          }        }      }      return uuid.join( ‘‘ ); }

Four ways to generate UUID for JS