在开发过程中，有时候需要js生成全局唯一标识符，在java中可以使用uuid，但是JS中没有现成的函数。总结了一下，JS生成唯一标识符的几种方法。

Npm下载

uuid

1. 安装

npm install uuid --save

2. 使用

import { v4 as uuidv4 } from 'uuid';
uuidv4(); # ⇨ '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'
# 或者
const { v4: uuidv4 } = require('uuid');
uuidv4(); # ⇨ '1b9d6bcd-bbfd-4b2d-9b5d-ab8dfbbd4bed'

ulid

1. 安装

npm install ulid --save

2. 使用

import { ulid } from 'ulid'
ulid() # 01ARZ3NDEKTSV4RRFFQ69G5FAV

# const ULID = require('ulid')
# ULID.ulid()

JS原生实现

第一种

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);
    });
}
guid() // "a1ca0f7b-51bd-4bf3-a5d5-6a74f6adc1c7"

第二种

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;
}
uuid() // "ffb7cefd-02cb-4853-8238-c0292cf988d5"

第三种

function guid2() {
    function S4() {
        return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1);
    }
    return (S4() + S4() + "-" + S4() + "-" + S4() + "-" + S4() + "-" + S4() + S4() + S4());
}
guid2() // "748eea29-f842-4af9-a552-e1e1aa3ed979"

第四种

// 指定长度和基数
function uuid2(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('');
}
uuid2(16, 16) // "277571702EE33E11"

第五种

/*
 * 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);
      }
    );
  };
})();

// 默认
Math.uuid()
// 指定长度
Math.uuid(4)
// 指定长度和基数，基数必须小于 62
// 第二个参数为 2 时生成2进制数，8为8进制数......
Math.uuid(8, 10)