promise 学习

1、https://sunxiunan.com/

 

Promise.resolve(1)
    .then(v => Promise.resolve(v + 1))
    .then(v => Promise.resolve(v + 3))
    .then(v => console.log(`First: ${v}`));
Promise.resolve(1)
    .then(v => v + 1)
    .then(v => Promise.resolve(v + 5))
    .then(v => console.log(`Second: ${v}`));
Promise.resolve(1)
    .then(v => v + 1)
    .then(v => v + 7)
    .then(v => console.log(`Third: ${v}`));

　　

 

 

 

2、

function asyncFunc() {
  return Promise.resolve(123);
}

function myFunc() {
  return asyncFunc().then(() => Promise.reject(456));
  //.then((res) => 'success: ' + res)
  // .catch((reason) => 'error: ' + reason)
  // .finally(() => console.log('im finally 123'));
}

async function myFunc2() {
  try {
    let data = await myFunc();
    console.log('data is --->', data);
  } catch (e) {
    console.log('data error is --->', e);
  }
}

myFunc2();