promise/async/await实例

    //test1
    let code=200;
    let p1=new Promise((resolve,reject)=>{
        setTimeout(()=>{
            if(code==200){
                resolve("成功！");
            }else{
                reject("失败！");
            }
        })
    })

    p1.then((res)=>{
        console.log(result)
    }).catch((res)=>{
        console.log(result)
    })

    //test2
    function request(method,url,data){
        let request=new XMLHttpRequest()
        return new Promise((resolve,reject)=>{
            request.onreadystatechange==function(){
                if(request.readyState==4){
                    resolve(request.responseText);
                }else{
                    reject(request.status)
                }
            }
            request.open(method.url)
            request.send(data)
        })
    }

    request("get","").then((result)=>{
        console.log(JSON.parse(result))
    }).catch((err)=>{
        console.log(err)
    })

    //test3
    function getTime(){
        return new Promise((resolve,reject)=>{
            setTimeout(()=>{
                resolve(10)
            },30)
        })
    }

    async function getAsync(){
        let num=await getTime();
        console.log(num)
    }