浅谈JS三座大山之异步和单线程

let fun1 = function(flag){
    return new Promise((resolve,reject)=>{
    if(flag){
        setTimeout(() => {
        resolve("success")
        }, 1000);
    }else{
        setTimeout(() => {
        reject("fail")
        }, 1000);
    }
    })
}
　　
fun1(true).then((res)=>{
    console.log(res)//success
}).catch((res)=>{
    console.log(res)
})
fun1(false).then((res)=>{
    console.log(res)
}).catch((res)=>{
    console.log(res)//fail
})

let callService = function(url){
      return new Promise((resolve,reject)=>{
          axiOS.get(url).then((res)=>{
            resolve(res)
          }).catch((err)=>{
            reject(err)
          })
      
      })
    }
    const url1 = "/user/url1"
    const url2 = "/user/url2"
    const url3 = "/user/url3"
    callService(url1).then((res)=>{
      // do something
      return callService(url2)
    }).then(()=>{
      // do something
      return callService(url3)
    }).then((res)=>{
      // do something
    }).catch((err)=>{
      console.log(err)
    })

let p1 = new Promise((resolve, reject) => {
  resolve('成功了')
})

let p2 = new Promise((resolve, reject) => {
  resolve('success')
})

Promise.all([p1, p2]).then((result) => {
  console.log(result)               //['成功了', 'success']
}).catch((error) => {
  console.log(error)
})

Promise.race([p1, p2]).then((result) => {
  console.log(result)
}).catch((error) => {
  console.log(error) 
})