requestAnimationFrame模拟定时器

	const {	myInterval, clearMyInterval } = (function(){
					// 存放系统中的定时器id
					        let timerIdMap = { num: 0 }
					        function myInterval(callback, interval) {
					            // 每设置一次定时器，num++ 代表系统中有num个自定义的定时器
					            timerIdMap.num ++
					            // 第 num 个定时器的id
					            let intervalId = 'id' + timerIdMap.num
					            timerIdMap[intervalId] = true;
					            // 循环次数
					            let count = 0
					            let startTime = Date.now();
					            let loop = () => {
					                // 系统map中不存在这个id，就停止循环
					                if (!timerIdMap[intervalId]) {
					                    return
					                }
					                if (Date.now() > startTime + interval * (count + 1)) {
					                    count++;
					                    callback(count)
					                }
					                window.requestAnimationFrame(loop)
					            }
					            loop()
					            return intervalId
					        }
					        // 清空定时器，删除全局的定时器id map
					        function clearMyInterval(intervalId) {
					            delete timerIdMap[intervalId]
					        }
							return {
								myInterval,
								clearMyInterval
							}
				}());
			        
			        // 调用定时器方法，返回定时器id，用于按条件清空
			        let timerId = myInterval((count) => {
			            console.log(count)
						
						fetch('xxxx',{
							method:"post"
						}).then(res => res.json()).then(res => {
							if(res.code ===0 && count ==5){
								clearMyInterval(timerId)
							}
						})
			       }, 2000)
				   
				   // 调用定时器方法，返回定时器id，用于按条件清空
				    let timerId2 = myInterval((count) => {
				        if (count > 15) {
				            clearMyInterval(timerId2)
				        }
				   }, 1000)