function generate(count) {
    var founded = false,
        _sym = 'abcdefghijklmnopqrstuvwxyz1234567890',
        str = '';
    while(!founded) {
        for(var i = 0; i < count; i++) {
            str += _sym[parseInt(Math.random() * (_sym.length))];
        }
        base.getID(string, function(err, res) {
            if(!res.length) {
                founded = true; // How to do it?
            }
        });
    }
    return str;
}

如何设置一个变量值与数据库查询回调?我该怎么做呢?


当前回答

这里是目前解决方案的一个基准,参考纳米基准

import { v4 as uuid4 } from 'uuid'
import benchmark from 'benchmark'
import shortid from 'shortid'

let suite = new benchmark.Suite()

suite
  .add('crypto.randomUUID', () => {
    crypto.randomUUID()
  })
  .add('nanoid', () => {
    nanoid()
  })
  .add('uuid v4', () => {
    uuid4()
  })
  .add("math.random", () => {
    (new Date()).getTime().toString(36) + Math.random().toString(36).slice(2)
  })
  .add('crypto.randomBytes', () => {
    crypto.randomBytes(32).toString('hex')
  })
  .add('shortid', () => {
    shortid()
  })
  .on('cycle', event => {
    let name = event.target.name
    let hz = formatNumber(event.target.hz.toFixed(0)).padStart(10)

    process.stdout.write(`${name}${pico.bold(hz)}${pico.dim(' ops/sec')}\n`)
  })
  .run()

结果是

node ./test/benchmark.js
crypto.randomUUID         13,281,440 ops/sec
nanoid                     3,278,757 ops/sec
uuid v4                    1,117,140 ops/sec
math.random                1,206,105 ops/sec
crypto.randomBytes           280,199 ops/sec
shortid                       30,728 ops/sec

测试env:

2.6 GHz 6Cores Intel酷睿i7 MacOS 节点v16.17.0

其他回答

让count = 0; 令previous = 0; const generateUniqueId = () => { const time = new Date().getTime() Count = time > previous ?0:(++计数) Const uid =时间+计数 Previous = uid 返回uid }

你可以使用urid包npm安装urid

import urid from 'urid';

urid(); // qRpky22nKJ4vkbFZ

阅读完整的文档:https://www.npmjs.com/package/urid

// Set the size
urid(8); //ZDJLC0Zq

// Use the character set
urid('num'); // 4629118294212196
urid('alpha'); // ebukmhyiagonmmbm
urid('alphanum'); // nh9glmi1ra83979b

// Use size with character set
urid(12, 'alpha'); // wwfkvpkevhbg

// use custom character set
urid(6, '0123456789ABCDEF'); // EC58F3
urid('0123456789ABCDEF'); // 6C11044E128FB44B

// some more samples
urid()               // t8BUFCUipSEU4Ink
urid(24)             // lHlr1pIzAUAOyn1soU8atLzJ
urid(8, 'num')       // 12509986
urid(8, 'alpha')     // ysapjylo
urid(8, 'alphanum')  // jxecf9ad

// example of all character sets
urid('num')          // 5722278852141945
urid('alpha')        // fzhjrnrkyxralgpl
urid('alphanum')     // l5o4kfnrhr2cj39w
urid('Alpha')        // iLFVgxzzUFqxzZmr
urid('ALPHA')        // ALGFUIJMZJILJCCI
urid('ALPHANUM')     // 8KZYKY6RJWZ89OWH
urid('hex')          // 330f726055e92c51
urid('HEX')          // B3679A52C69723B1

// custom character set
urid('ABCD-')        // ACA-B-DBADCD-DCA

从14.17.0开始,你现在可以使用内置的加密模块来生成uuid (UUIDv4 flavour):

const { randomUUID } = require('crypto'); // Added in: node v14.17.0

console.log(randomUUID());

// '89rct5ac2-8493-49b0-95d8-de843d90e6ca'

你可以探索更多 https://nodejs.org/api/crypto.html#crypto_crypto_randomuuid_options

注意:密码。randomUUID比uuid快三倍。而且不需要增加额外的依赖。

从YaroslavGaponov的答案延伸出来,最简单的实现就是使用Math.random()。

Math.random()

从数学上讲,分数在实空间[0,1]中相同的概率理论上为0。在node.js中,它的默认长度为16个小数,概率接近于0。这种实现还应该减少算术溢出,因为不执行任何操作。此外,与字符串相比,它的内存效率更高,因为小数占用的内存比字符串少。

我称之为“分数-唯一id”。

编写代码生成1,000,000个Math.random()数字,但无法找到任何重复的数字(至少对于默认的小数点为16)。参见下面的代码(如果有请提供反馈):

random_numbers = [] 
for (i = 0; i < 1000000; i++) { 
   random_numbers.push(Math.random()); 
   //random_numbers.push(Math.random().toFixed(13)) //depends decimals default 16 
} 

if (i === 1000000) { 
   console.log("Before checking duplicate"); 
   console.log(random_numbers.length); 
   console.log("After checking duplicate"); 
   random_set = new Set(random_numbers); // Set removes duplicates
   console.log([...random_set].length); // length is still the same after removing
} 

简单,基于时间,没有依赖:

(new Date()).getTime().toString(36)

or

Date.now().toString(36)

输出:jzlatihl


加上随机数(感谢@Yaroslav Gaponov的答案)

(new Date()).getTime().toString(36) + Math.random().toString(36).slice(2)

jzlavejjperpituute输出