[英]Why am I getting Promise { <pending> } when using fetch in Promise.all?
這很好用:
....
.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}));
})
但是當我嘗試將獲取與另一個承諾結合在一起時:
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}));
})
我得到Promise { <pending> }
作為輸出,似乎Promise.all在call()
完成之前就運行了
您必須在res[1].json()
.then()
上使用.then()
,因為它僅返回一個承諾,並且您無需在任何地方等待該承諾。
我建議您更改為:
let call = fetch(link, { headers: {"Content-Type": "application/json; charset=utf-8"} })
.then(response => response.json());
然后,您的call
變量已經使.json()
調用和Promise.all()
將等待它。
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]);
});
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