Promise面试题

const promise1 = new Promise((resolve, reject) => {
  console.log('promise1')
})
console.log('1', promise1);

输出

'promise1'
'1' Promise{<pending>}

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);

输出

'promise1'
'1' Promise{<resolved>: 'resolve1'}
'2' Promise{<pending>}
'resolve1'