定时器实现Promis.all()的简单使用

// 异步事件1
function time1() {
    const promise = new Promise(function (resolve, reject) {
        setTimeout(function () {
            resolve("timer1执行完毕")
        }, 1000)
    })
    return promise
}

// 异步事件2
function time2() {
    const promise = new Promise(function (resolve, reject) {
        setTimeout(function () {
            resolve("timer2执行完毕")
        }, 2000)
    })
    return promise
}

// 异步事件3
function time3() {
    const promise = new Promise(function (resolve, reject) {
        setTimeout(function () {
            resolve("timer3执行完毕")
        }, 3000)
    })
    return promise
}

console.log("程序开始执行，计时开始....")
console.time('程序运行耗时为')

let t1 = time1()
let t2 = time2()
let t3 = time3()

Promise.all([t1, t2, t3]).then(datas => {
    console.log(datas[0])
    console.log(datas[1])
    console.log(datas[2])
    console.log(`全部执行完毕`)
    console.timeEnd('程序运行耗时为')
})

效果图：