1. pending，resolved（fulfilled），reject

    <script>
        /* 
        then之后的返回值的状态 resolved,如果遇到错误,状态会变成reject
        Tips:  then只能触发promise-->resolved的状态
         */
        var p = Promise.resolve(100).then((res) => {
            console.log(res)
            throw "err"
        })
        p.then(()=>{
            console.log(200)
        })
    </script>

2 状态的切换

3 用async时候，await不能接收reject

    <script>
        /* 
        await只能得到Promise--resolved状态的结果,作用相当于then函数
         */
        (async ()=>{
            var p = Promise.reject(100);
            var res = await p;
            console.log(res)
        })();
        /* Promise.reject(err).catch()捕获异常 */
    </script>

所以要结合try和catch来获取

    <script>
        (async ()=>{
            var p = Promise.reject("err");
            try{
                let res = await p;
                console.log(res)
            }catch(err){
                console.log(err)
            }
        })();
        /* 
        在async-await中可以使用try-catch语句去捕获异常
        Promise.reject("err").catch()
         */
    </script>