promise不會被return觸發， 一個promise對象中不會被Promise.reject觸發

1.

let a = new Promise((resolve,reject)=>{

　　return 23

})

 

a; // promise <pending>

 

2.

let a = new Promise((resolve,reject)=>{

　　Promise.reject(234)

})

a; // promise <pending>

 

3.

let a = new Promise((resolve,reject)=>{

　　return Promise.reject(12)

}

a; //promise <pending> 

 

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/reject