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https://github.com/leejialing/limit-promise

Run multiple promise-returning & async functions with limited concurrency
https://github.com/leejialing/limit-promise

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Run multiple promise-returning & async functions with limited concurrency

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# limit promise

EN:  

Run multiple promise-returning & async functions with limited concurrency



CN:  

Promise执行数量控制，即"并发"控制（众所周知js是单线程，并不存在真正的并发，只是形象说明才这么称呼的）。



应用场景如：控制异步请求的数量。



## Install (安装)



`npm install limit-promise --save`  

or  

`yarn add limit-promise`



## Tip

EN:  

Make sure that the function you want to execute is:

* returns a Promise that matches the Promise criteria

* async function

* make sure Promise resolves or reject, otherwise it will "block" the call queue



If it doesn't meet the standard, please adapt yourself



CN:  

确保需要执行的函数是：

* 返回一个符合Promise标准的promise

* async函数

* 确保Promise会resolve或者reject，否则会"阻塞"住调用队列。



如果不符合标准请自行适配一下。



## Usage（使用）



```js



// request.js

// a request module, contain 'get' and 'post' function



// limitRequest.js

const LimitPromise = require('limit-promise')

const request = require('./request')

// request maximum limit 并发请求上限

const MAX = 5

// core controller 核心控制器

const limitP = new LimitPromise(MAX)



// 通过控制器包装get和post方法，实际上是将请求函数递交给控制器处理

// Wrapping the get and post methods with the controller,

// The request function is actually handed over to the controller for processing

function get (url, params) {

  return limitP.call(request.get, url, params)

}



function post (url, params) {

  return limitP.call(request.post, url, params)

}



module.exports = {get, post}



// example.js



// import new request module

const request = require('./limitRequest')

// mock apis

const apis = [

  {url: 'www.baidu.com'},

  {url: 'www.taobao.com'},

  {url: 'www.qq.com'},

  {url: 'www.jd.com'},

  {url: 'www.meituan.com'},

  {url: 'www.toutiao.com'},

  {url: 'www.weibo.com'},

  {url: 'www.zhihu.com'},

  {url: 'www.alipay.com'}

]



// start multiple network request

// Because the maximum number of requests is limited to 5, the first five requests will start immediately, and the sixth will start in the ready queue for execution

// Once a request is completed and returned, a task is removed from the queue for execution

// 简单粗暴的使用for循环启动数个请求

// 由于限制了最大请求数量是5，因此前五个请求将立即启动，而第6个开始将进入就绪队列等待执行

// 一旦某个请求结束并返回，将从队列中取下一个任务执行

for (let i = 0; i < apis.length; i++) {

  request.get(apis[i].url, {id: i})

    .then(res => console.log(`request resolve : ${res}`))

}



```



## License

*MIT*