写一个函数，可以控制最大并发数

function concurrentPoll(){
    this.tasks = [];
    this.max = 10;
    setTimeout(() => {
        this.run()
    },0)
}

concurrentPoll.prototype.addTask = function(task){
    this.tasks.push(task)
}

concurrentPoll.prototype.run = function(){
    if(this.tasks.length == 0){
        return
    }
    var min = Math.min(this.tasks.length, max);
    for(var i = 0; i < min; i++){
        this.max--;
        var task = this.tasks.shift();
        task().then((res) => {
            console.log(res)
        }).catch((err) => {
            console.log(err)
        }).finally(() => {
            this.max++;
            this.run();
        })
    }
}