js控制最大并发数

使用场景： 1.maxLength为1，可以控制发送顺序 2.性能优化，控制并发数量，减少对服务端的冲击

注意：1.arr装函数 2.每个函数要有个对应的index 3.要有结果arr 4.通过resolve传递

class Task {

  taskArr = [];
  limit = 1;
  result = [];
  nextIndex = 0;
  constructor(limit = 1) {
    this.limit = limit;
  }
  async nextRun(resolve) {
    // const current = this.currentIndex++;
    const current = this.nextIndex++;
    // console.log("result", "res");
    if (!this.result.includes(false)) {
      return resolve(this.result);
    }
    try {
      const res = await this.taskArr[current]();
      // console.log("result", res);
      this.result[current] = res;
    } catch (error) {
      this.result[current] = error;
      // console.log("result", "error", error);
    }
    this.nextRun(resolve);
  }
  run() {
    this.result =
      [false, false, false, false, false] ||
      new Array(this.taskArr.length).fill(false);

    return new Promise((resolve, reject) => {
      while (this.nextIndex <= this.limit) {
        //外层的同步会忽略里层的async await 还是将其做同步处理
        this.nextRun(resolve);
      }
    });
  }
  setTaskArr(arr) {
    if (Array.isArray(arr)) {
      arr.forEach((r) => {
        if (r instanceof Function) {
          return;
        }
        throw Error("请传入函数");
      });
    }
    this.taskArr = arr;
    return this.run();
  }
}
const f = () => {
  return new Promise((res, rej) => {
    console.log();
    setTimeout(() => {
      res("11111");
    }, 2000);
  });
};
new Task(2).setTaskArr([f, f, f, f, f, f, f]).then((res) => {
  console.log(res, ":res");
});