async await

await等待的是Promise的 resolve和reject(axios能用实际上axios封装的是Promise)

function sleep(second) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            resolve('sleep~');
        }, second);
    })
}

function normalFunc() {
    setTimeout(()=>{
        console.log('normalFunc');
    },3000)
}

async function awaitDemo() {
    await normalFunc();
    let result = await sleep(2000);
    console.log(result);// 两秒之后会被打印出来
    console.log('something, ~~');
}

awaitDemo();
// sleep~
// something, ~~
// normalFunc
//因为async中的await只等待Promise的 resolve和reject，所以normalFunc没有被等待，而sleep被等待了