class Scheduler {constructor(max = 2) {// 最大运行数量this.maxNum = max// 当前运行数量this.runNum = 0// 事件队列this.runlist = []this.resolve = null// 运行完成的数量this.complateNum = 0}getRes(list, max) {this.list = listthis.maxNum = maxthis.result = []return new Promise((resolve, reject) => {this.resolve = resolve// 如果事件队列中的事件数量为0，直接返回结果if (this.list.length === 0) {this.resolve(this.result)return}this.runList()})}runList() {// 因为最后的结果需要按照顺序返回，所有给每个事件增加一个下标，用来存值for (let i = 0; i < this.list.length; i++) {this.runlist.push({index: i, cb: this.list[i]})}this.run()}run() {// 如果当前正在运行的数量小于最大运行数量，并且事件列表中有值while (this.runNum < this.maxNum && this.runlist.length) {// 从事件列表中取第一项的值然后运行let itempro = this.runlist.shift()let cb = itempro.cblet index = itempro.indexthis.runNum++cb.then(res => {this.result[index] = res}).catch(err => {this.result[index] = err}).finally(() => {this.complateNum++this.runNum--console.log(this.result)// 当所有的事件执行完成以后返回值if (this.complateNum == this.list.length) {this.resolve(this.result)} else {this.run()}})}}}
let proArr = []for (let i = 0; i < 100; i++) {let randomTime = Math.floor(Math.random() * 10) + 1proArr.push(new Promise((resolve) => {//模拟接口调用setTimeout(() => {resolve('-------'+i+'--------'+randomTime)}, randomTime*1000)}) )
}let scheduler = new Scheduler()
scheduler.getRes(proArr, 2).then(res => {console.log('res', res)
})