1-2-1 await

1.await会执行promise的resolve的状态,相当于执行了then函数

                async function a1(){
            console.log("a1-start")
            await a2();
            console.log("a1-end")
        }
        async function a2(){
            console.log("a2")
        }
        a1();
        console.log("end-script")

await会将函数阻塞,会优先执行同步不耗时的任务

async function show(){
    console.log("start");
    await mid();
    console.log("end")
}
async function mid(){
    console.log("mid")
}
show()
console.log("line")

async function a1() {
    console.log("a1-start")
    await a2();
    console.log("a1-end")
}
async function a2() {
    console.log("a2")
}
a1();
console.log("end-script")
new Promise((resolve) => {
    console.log("a3")
    resolve()
}).then(() => {
    console.log("a4")
})

await后面的代码可以看做是一个异步回调