1. 异步 %26 事件循环

密码：answer

一、异步 && 事件循环

1、 阅读代码

const promise = new Promise((resolve, reject) => {
  console.log(1);
  console.log(2);
});
promise.then(() => {
  console.log(3);
});
console.log(4);

2、阅读代码

const promise1 = new Promise((resolve, reject) => {
  console.log('promise1')
  resolve('resolve1')
})
const promise2 = promise1.then(res => {
  console.log(res)
})
console.log('1', promise1);
console.log('2', promise2);

3、 阅读代码

Promise.resolve().then(() => {
  console.log('promise1');
  const timer2 = setTimeout(() => {
    console.log('timer2')
  }, 0)
});
const timer1 = setTimeout(() => {
  console.log('timer1')
  Promise.resolve().then(() => {
    console.log('promise2')
  })
}, 0)
console.log('start');

4、 阅读代码

const promise = new Promise((resolve, reject) => {
  console.log(1);
  setTimeout(() => {
    console.log("timerStart");
    resolve("success");
    console.log("timerEnd");
  }, 0);
  console.log(2);
});
promise.then((res) => {
  console.log(res);
});
console.log(4);

5、 阅读代码

const promise = new Promise((resolve, reject) => {
    resolve('success1');
    reject('error');
    resolve('success2');
});
promise.then((res) => {
    console.log('then:', res);
}).catch((err) => {
    console.log('catch:', err);
})

6、 阅读代码

Promise.resolve(1)
  .then(2)
  .then(Promise.resolve(3))
  .then(console.log)

7、 阅读代码

const promise1 = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('success')
  }, 1000)
})
const promise2 = promise1.then(() => {
  throw new Error('error!!!')
})
console.log('promise1', promise1)
console.log('promise2', promise2)
setTimeout(() => {
  console.log('promise1', promise1)
  console.log('promise2', promise2)
}, 2000)

8、 阅读代码

Promise.resolve(1)
  .then(res => {
    console.log(res);
    return 2;
  })
  .catch(err => {
    return 3;
  })
  .then(res => {
    console.log(res);
  });

9、 阅读代码

Promise.resolve().then(() => {
  return new Error('error!!!')
}).then(res => {
  console.log("then: ", res)
}).catch(err => {
  console.log("catch: ", err)
})

10、 阅读代码

const promise = Promise.resolve().then(() => {
  return promise;
})
promise.catch(console.err)

11、 阅读代码

Promise.resolve(1)
  .then(2)
  .then(Promise.resolve(3))
  .then(console.log)

12、 阅读代码

Promise.reject('err!!!')
  .then((res) => {
    console.log('success', res)
  }, (err) => {
    console.log('error', err)
  }).catch(err => {
    console.log('catch', err)
  })

13、 阅读代码

Promise.resolve('1')
  .then(res => {
    console.log(res)
  })
  .finally(() => {
    console.log('finally')
  })
Promise.resolve('2')
  .finally(() => {
    console.log('finally2')
      return '我是finally2返回的值'
  })
  .then(res => {
    console.log('finally2后面的then函数', res)
  }) 6

14、 阅读代码

function runAsync (x) {
    const p = new Promise(r => setTimeout(() => r(x, console.log(x)), 1000))
    return p
}
Promise.all([runAsync(1), runAsync(2), runAsync(3)]).then(res => console.log(res))

15、 阅读代码

function runAsync (x) {
  const p = new Promise(r => setTimeout(() => r(x, console.log(x)), 1000))
  return p
}
function runReject (x) {
  const p = new Promise((res, rej) => setTimeout(() => rej(`Error: ${x}`, console.log(x)), 1000 * x))
  return p
}
Promise.all([runAsync(1), runReject(4), runAsync(3), runReject(2)])
       .then(res => console.log(res))
       .catch(err => console.log(err))

16、 阅读代码

function runAsync (x) {
  const p = new Promise(r => setTimeout(() => r(x, console.log(x)), 1000))
  return p
}
Promise.race([runAsync(1), runAsync(2), runAsync(3)])
  .then(res => console.log('result: ', res))
  .catch(err => console.log(err))

17、 阅读代码

function runAsync(x) {
  const p = new Promise(r =>
    setTimeout(() => r(x, console.log(x)), 1000)
  );
  return p;
}
function runReject(x) {
  const p = new Promise((res, rej) =>
    setTimeout(() => rej(`Error: ${x}`, console.log(x)), 1000 * x)
  );
  return p;
}
Promise.race([runReject(0), runAsync(1), runAsync(2), runAsync(3)])
  .then(res => console.log("result: ", res))
  .catch(err => console.log(err));

18、 阅读代码

async function async1() {
  console.log("async1 start");
  await async2();
  console.log("async1 end");
}
async function async2() {
  console.log("async2");
}
async1();
console.log('start')

19、 阅读代码

async function async1() {
  console.log("async1 start");
  await async2();
  console.log("async1 end");
  setTimeout(() => {
    console.log('timer1')
  }, 0)
}
async function async2() {
  setTimeout(() => {
    console.log('timer2')
  }, 0)
  console.log("async2");
}
async1();
setTimeout(() => {
  console.log('timer3')
}, 0)
console.log("start")

20、 阅读代码

async function async1 () {
  console.log('async1 start');
  await new Promise(resolve => {
    console.log('promise1')
  })
  console.log('async1 success');
  return 'async1 end'
}
console.log('srcipt start')
async1().then(res => console.log(res))
console.log('srcipt end')

21、 阅读代码

async function async1 () {
  console.log('async1 start');
  await new Promise(resolve => {
    console.log('promise1')
    resolve('promise1 resolve')
  }).then(res => console.log(res))
  console.log('async1 success');
  return 'async1 end'
}
console.log('srcipt start')
async1().then(res => console.log(res))
console.log('srcipt end')

22、 阅读代码

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

23、 阅读代码

async function async1 () {
  await async2();
  console.log('async1');
  return 'async1 success'
}
async function async2 () {
  return new Promise((resolve, reject) => {
    console.log('async2')
    reject('error')
  })
}
async1().then(res => console.log(res))

24、 阅读代码

const first = () => (new Promise((resolve, reject) => {
    console.log(3);
    let p = new Promise((resolve, reject) => {
        console.log(7);
        setTimeout(() => {
            console.log(5);
            resolve(6);
            console.log(p)
        }, 0)
        resolve(1);
    });
    resolve(2);
    p.then((arg) => {
        console.log(arg);
    });
}));
first().then((arg) => {
    console.log(arg);
});
console.log(4);

25、 阅读代码

const async1 = async () => {
  console.log('async1');
  setTimeout(() => {
    console.log('timer1')
  }, 2000)
  await new Promise(resolve => {
    console.log('promise1')
  })
  console.log('async1 end')
  return 'async1 success'
} 
console.log('script start');
async1().then(res => console.log(res));
console.log('script end');
Promise.resolve(1)
  .then(2)
  .then(Promise.resolve(3))
  .catch(4)
  .then(res => console.log(res))
setTimeout(() => {
  console.log('timer2')
}, 1000)

26、 阅读代码

const p1 = new Promise((resolve) => {
  setTimeout(() => {
    resolve('resolve3');
    console.log('timer1')
  }, 0)
  resolve('resovle1');
  resolve('resolve2');
}).then(res => {
  console.log(res)  // resolve1
  setTimeout(() => {
    console.log(p1)
  }, 1000)
}).finally(res => {
  console.log('finally', res)
})

27、 阅读代码

console.log('1');
setTimeout(function() {
    console.log('2');
    process.nextTick(function() {
        console.log('3');
    })
    new Promise(function(resolve) {
        console.log('4');
        resolve();
    }).then(function() {
        console.log('5')
    })
})
process.nextTick(function() {
    console.log('6');
})
new Promise(function(resolve) {
    console.log('7');
    resolve();
}).then(function() {
    console.log('8')
})
setTimeout(function() {
    console.log('9');
    process.nextTick(function() {
        console.log('10');
    })
    new Promise(function(resolve) {
        console.log('11');
        resolve();
    }).then(function() {
        console.log('12')
    })
})

28、 阅读代码

console.log(1)
setTimeout(() => {
  console.log(2)
})
new Promise(resolve =>  {
  console.log(3)
  resolve(4)
}).then(d => console.log(d))
setTimeout(() => {
  console.log(5)
  new Promise(resolve =>  {
    resolve(6)
  }).then(d => console.log(d))
})
setTimeout(() => {
  console.log(7)
})
console.log(8)

29、 阅读代码

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

30、 阅读代码

Promise.resolve().then(() => {
    console.log('1');
    throw 'Error';
}).then(() => {
    console.log('2');
}).catch(() => {
    console.log('3');
    throw 'Error';
}).then(() => {
    console.log('4');
}).catch(() => {
    console.log('5');
}).then(() => {
    console.log('6');
});

31、 阅读代码

setTimeout(function () {
  console.log(1);
}, 100);
new Promise(function (resolve) {
  console.log(2);
  resolve();
  console.log(3);
}).then(function () {
  console.log(4);
  new Promise((resove, reject) => {
    console.log(5);
    setTimeout(() =>  {
      console.log(6);
    }, 10);
  })
});
console.log(7);
console.log(8);