async function getData(){
        let res1 = await $.ajax({url:'data/arr.txt',dataType:'json'})
        let res2 = await $.ajax({url:'data/json.txt',dataType:'json'})
        console.log(res1,res2)
    }
    getData()

let foo = await getFoo();
let bar = await getBar();

这样比较耗时，因为只有getFoo完成以后，才会执行getBar，完全可以让它们同时触发：

// 写法一
let [foo, bar] = await Promise.all([getFoo(), getBar()]);

// 写法二
let fooPromise = getFoo();
let barPromise = getBar();
let foo = await fooPromise;
let bar = await barPromise;

1.继发执行异步

async function logInOrder(urls) {
  for (const url of urls) {
    const response = await fetch(url);
    console.log(await response.text());
  }
}

2.并发执行异步

async function logInOrder(urls) {
  // 并发读取远程URL
  const textPromises = urls.map(async url => {
    const response = await fetch(url);
    return response.text();
  });

  // 按次序输出
  for (const textPromise of textPromises) {
    console.log(await textPromise);
  }
}