JavaScript Promise的使用

const promise = new promise(function(resolve, reject){
    if(/* 异步操作成功 */){
        resolve(value)
    }else{
        reject(error)
    }
})

promise.then(function(value){
    //success
}else{
    // false
})

const p = new Promise((resolve, reject)=>{
    //resolve(‘失败的结果‘)
    reject(‘失败的结果‘)
})

p.then(()=>{
    console.log(‘成功时调用‘)
}, () =>{
    console.log(‘失败时调用‘)
})
console.dir(p)
// 如果then写在Promise后面并且调用resolve()则不会执行第一个then

const p1 = new Promise(function (resolve, reject) {
  // ...
});

const p2 = new Promise(function (resolve, reject) {
  // ...
  resolve(p1);
})