异步执行```js ```async function async1() { console.log("async1 s

```async function async1() {
    console.log("async1 start");
    await async2();
    console.log("async1 end");
    setTimeout(() => {
        console.log('timer1')
    }, 0)
}
async function async2() {
    setTimeout(() => {
        console.log('timer2')
        Promise.resolve().then(() => {
            console.log('1---');
        })
    }, 0)
    console.log("async2");
}
async1();
setTimeout(() => {
    console.log('timer3')
}, 0)
console.log("start") 

输出： 
async1 start     async2     start    async1 end         timer2    1---    timer3   timer1