第一题

time 0

 await async2();
    console.log('async1 end');

await async2();返回promise，等待，相当于以下代码，把await之后的全部放then里面，多个await就是then链式调用

async2().then(() => {console.log('async1 end')})

async function async1() {
    console.log('async1 start');
    /**
     * Promise1
     * async2().then(() => {console.log('async1 end')})
     ***/
    await async2();
    console.log('async1 end');
}
async function async2() {
    console.log('async2');
}
console.log('script start');
// setTimeout1
setTimeout(function () {
    console.log('setTimeout');
}, 0);
async1();
new Promise(function (resolve) {
    console.log('promise1');
    resolve();
})
    // Promise2
    .then(function () {
        console.log('promise2');
    })
console.log('script end');

第2题

time 6m46s
async2().then(()=>{console.log(‘async1 end’)});，先执行async2()，打印promise1，添加promise1.then cb，再执行.then,添加awaitPromise1 cb，这个其实不是then的链式调用

async function async1() {
    console.log('async1 start');
    /**
    * awaitPromise1
    * async2().then(()=>{console.log('async1 end')});
    * 
    ***/
    await async2();
    console.log('async1 end');
}
async function async2() {
    new Promise(function (resolve) {
        console.log('promise1');
        resolve();
    })
    // Promsie1
        .then(function () {
        console.log('promise2');
    });
}
console.log('script start');
// setTimeout1
setTimeout(function () {
    console.log('setTimeout');
}, 0)
async1();
new Promise(function (resolve) {
    console.log('promise3');
    resolve();
})
// Promise2
    .then(function () {
    console.log('promise4');
});
console.log('script end');

执行栈
script start
async1(）->async1 start
async2()->promise1
promise3
script end
Promsie1.then cb 2th->promise2
Promsie1.then cb 2th->async1 end
Promise2.then cb 4th->promise4
setTimeout1 cb 1th->setTimeout

微任务
Promsie1
Promsie1.then cb 2th x
awaitPromise1
awaitPromise1.then cb 3th x
Promise2
Promise2.then cb 4th
宏任务
setTimeout1
setTimeout1 cb 1th

async function async1() {
    console.log('async1 start');
    /**
     * awaitPromise1
     * async2().then(()=>{console.log('async1 end')});
     *
     ***/
    await async2();
    console.log('async1 end');
}
async function async2() {
    new Promise(function (resolve) {
        console.log('promise1');
        resolve();
    })
        // Promsie1
        .then(function () {
            console.log('promise2');
        })
          // Promsie1-2
        .then(function () {
            console.log('promise2-2');
        });
}
console.log('script start');
// setTimeout1
setTimeout(function () {
    console.log('setTimeout');
}, 0)
async1();
new Promise(function (resolve) {
    console.log('promise3');
    resolve();
})
    // Promise2
    .then(function () {
        console.log('promise4');
    })
    .then(function () {
        console.log('promise4-2');
    });
console.log('script end');

证明了 async2().then(()=>{console.log(‘async1 end’)});不是链式调用，因为在Promsie1-2 cb之前awaitPromise1就运行了

第三题

time 12m12s

第3题

time 19m18s

var promise = new Promise((resolve) => {
    console.log(1);
    resolve();
});
// setTimeout1
setTimeout(() => {
    console.log(2);
});
// Promise1
promise.then(() => {
    console.log(3);
});
var promise2 = getPromise();
async function getPromise() {
    console.log(5);
    /**
     * awaitPromise
     * 因为await promise本身就是promise
     * promise.then(()=>{console.log(6)})
     **/
    await promise;
    console.log(6);
}
console.log(8);

第4题

time 25m25s
多次调用eat方法

const LazyMan = function (name) {
    console.log(`Hi i am ${name}`);
    function _eat(food) {
        console.log(`I am eating ${food}`);
    }
    const callbacks = [];
    class F {
        sleep(timeout) {
            setTimeout(function () {
                console.log(`等待了${timeout}秒....`);
                console.log(callbacks);
                callbacks.forEach(cb => cb())
            }, timeout);
            return this;
        };
        eat(food) {
            callbacks.push(_eat.bind(null, food));
            return this;
        }
    }
    return new F();
};
LazyMan('Tony').sleep(10).eat('lunch').eat('meal');