JavaScript中的Promise详解

let promise = new Promise((resolve,reject)=>{
    ajax('first').success(function(res){
        resolve(res);
    })
})
promise.then(res=>{
    return new Promise((resovle,reject)=>{
        ajax('second').success(function(res){
            resolve(res)
        })
    })
}).then(res=>{
    return new Promise((resovle,reject)=>{
        ajax('second').success(function(res){
            resolve(res)
        })
    })
}).then(res=>{
 })

p.then((data) => {
     console.log('resolved',data);
},(err) => {
     console.log('rejected',err);
     }
); 
p.then((data) => {
    console.log('resolved',data);
}).catch((err) => {
    console.log('rejected',err);
});

javascript
let promise1 = new Promise((resolve,reject)=>{
	setTimeout(()=>{
       resolve(1);
	},2000)
});
let promise2 = new Promise((resolve,reject)=>{
	setTimeout(()=>{
       resolve(2);
	},1000)
});
let promise3 = new Promise((resolve,reject)=>{
	setTimeout(()=>{
       resolve(3);
	},3000)
});
Promise.all([promise1,promise2,promise3]).then(res=>{
    console.log(res);
    //结果为：[1,2,3] 
})

Promise.race([promise1,timeOutPromise(5000)]).then(res=>{})

promise
.then(result => {···})
.catch(error => {···})
.finally(() => {···});

promise
.finally(() => {
  // 语句
});
// 等同于
promise
.then(
  result => {
    // 语句
    return result;
  },
  error => {
    // 语句
    throw error;
  }
);