Promise并发量控制

let self = this;
new Promise(resolve => {
  let index = 0
  let timer = null;
  let stepCount = 2 // 并行n个
  let result = [] // 数据存放
  let count = promises.length
  if (promises.length === 0) {
    resolve(result)
  } else {
    function runPromise() {
      let promise = []
      if (index === promises.length) {
        resolve(result);
      } else {
        stepCount = Math.min(count, stepCount)
        for (let i = 0; i < stepCount; i++) {
          promise.push(promises[index])
          --count;
          index++
        }
        let _count = 0;
        function loop(){
          Promise.all(promise.map(n=>{
            return axios(n)
          })).then(res=>{
            _count = 0
            timer = null
            let data = []
            for (let i = 0; i < res.length; i++) {
              data.push(res[i].data)
            }
            result = [...result,...data]
            runPromise()
          }).catch((err)=>{
            console.log(err)
            _count+=1
            if(_count > 4){
              self.$message.warning('重试次数达到4次')
              console.log(err)
              return false
            }
            self.$message.warning('正常重试，次数'+_count)
            timer = setTimeout(()=>{
              loop()
            },1000)
          })
        }
        loop()
      }
    }
    runPromise()
  }
})