输出是什么


Promise.resolve().then(() => {
  console.log(1);
 
  Promise.resolve().then(() => {
    console.log(2);
  });
 
}).then(() => {
  console.log(3);
});
 
console.log(4);

输出是什么


console.log('x');
 
setTimeout(() => {
  console.log('y');
  Promise.resolve().then(() => {
    console.log('z');
  });
}, 0);
 
Promise.resolve().then(() => {
  console.log('p');
});
 
console.log('q');

输出是什么


console.log(1);
 
setTimeout(() => {
  console.log(2);
 
  Promise.resolve().then(() => {
    console.log(3);
  });
 
}, 0);
 
Promise.resolve().then(() => {
  console.log(4);
 
  setTimeout(() => {
    console.log(5);
  }, 0);
});
 
setTimeout(() => {
  console.log(6);
}, 0);
 
console.log(7);

4.输出是什么


async function test() {
  console.log(1);
 
  await Promise.resolve();
  console.log(2);
 
  setTimeout(() => {
    console.log(3);
  }, 0);
 
  await 4;
  console.log(5);
}
 
console.log(6);
 
test();
 
Promise.resolve().then(() => {
  console.log(7);
});
 
setTimeout(() => {
  console.log(8);
}, 0);
 
console.log(9);

输出是什么


        async function fn() {
            //创建一个promise
            console.log('start');
            let isSuccess = await new Promise((res, rej) => {
                console.log('3');
                // 异步操作
                setTimeout(() => {
                    console.log("定时器完成")
                    res(1)
                }, 0)
            })
            console.log('end');
            // console.log(isSuccess);
        }
        console.log(1);
        fn()
        console.log(2);

这里的执行顺序是 1 start

然后await执行 new Promise

new Promise 的执行器同步执行 → 打印 3

执行器内的 setTimeout 注册一个宏任务（0ms）

async 函数在 await 处暂停，剩余代码保存起来（不会加入微任务队列，等待 Promise resolve）

也就是说 await会等待后面的promise完成之后再将后续代码放入微任务队列现在暂时跳出async函数

打印2

然后宏任务队列定时器完成打印定时器完成

➡ 使 Promise resolved ➡ 触发 await 的恢复逻辑

然后await检测到promise完成将后续代码放入微任务队列

也就是执行end

输出是什么


//如果await后是new Promise 先执行里面同步代码 然后暂停
//如果是Promise.resolve().then()就把then放到微任务队尾 然后暂停
//如果是Promise.resolve(0) 则直接把await下面的代码包装成微任务放入队尾
async function task1() {
  console.log('A');
 
  await Promise.resolve().then(() => {
    console.log('B');
  });
 
  console.log('C');
 
  await 0;
 
  console.log('D');
}
 
async function task2() {
  console.log('E');
 
  await task1();
 
  console.log('F');
}
 
console.log('G');
 
task2();
 
Promise.resolve().then(() => {
  console.log('H');
}).then(() => {
  console.log('I');
});
 
console.log('J');
 
 
//g e  a j b h c     i d f

输出是什么


async function alpha() {
    console.log('A');
 
    await Promise.resolve().then(() => {
        console.log('B');
    });
 
    console.log('C');
 
    await 0;
 
    console.log('D');
}
 
async function beta() {
    console.log('E');
 
    await alpha();
 
    console.log('F');
 
    await Promise.resolve();
 
    console.log('G');
}
 
console.log('H');
 
beta();
 
Promise.resolve().then(() => {
    console.log('I');
}).then(() => {
    console.log('J');
});
 
console.log('K');