Why am I getting Promise { } when using

问题:

This works fine:

....
.then(() => fetch(link, { headers: {"Content-Type": "application/json; charset=utf-8"} }))
  .then( res =>  res.json())
  .then((response)=>{
    console.log(util.inspect(response, {showHidden: true, depth: null, colors: true}));
  })

But whenI try to combine the fetch with another promise:

let dbconnect = require('mongodb').MongoClient.connect("mongodb://localhost:27017/mydb", { useNewUrlParser: true } ),
    call = fetch(link, { headers: {"Content-Type": "application/json; charset=utf-8"} });


Promise.all( [dbconnect, call] )
  .then( res => [res[0], res[1].json()])
  .then( res => {
    database = res[0];
    sales = res[1];
    console.log(util.inspect(res[1], {showHidden: true, depth: null, colors: true}));
  })

I get Promise { <pending> } as the output, it seems as though the Promise.all get run before call() is completed

回答1:

You have to use .then() on res[1].json() because it just returns a promise and you aren't waiting on that promise anywhere.

What I would suggest is that you change to this:

let call = fetch(link, { headers: {"Content-Type": "application/json; charset=utf-8"} })
    .then(response => response.json());

Then, your call variable has already made the .json() call and Promise.all() will wait on it for you.

---

let dbconnect = require('mongodb').MongoClient.connect("mongodb://localhost:27017/mydb", { useNewUrlParser: true } ),
    call = fetch(link, { headers: {"Content-Type": "application/json; charset=utf-8"} })
              .then(response => response.json());

Promise.all( [dbconnect, call] ).then( res => {
    console.log(res[0]);
    console.log(res[1]);
});