嵌套promises節點js

Question

我從here閱讀教程，我不明白爲什麼第二個「insertOne」不起作用。感謝幫助！

var Promise=require('promise'); 
var MongoClient=require('mongodb').MongoClient; 
var url = 'mongodb://localhost/EmployeeDB'; 
MongoClient.connect(url) 
    .then(function(db) 
{ 
    db.collection('Documents').insertOne({ 
     Employeeid: 1, 
     Employee_Name: "Petro"}) 
     .then(function(db1) { 
      db1.collection('Documents').insertOne({ 
       Employeeid: 2, 
       Employee_Name: "Petra"}) 
     }) 
     db.close(); 
    }); 

Answer 1

發生了兩個異步操作（db.insertOne）。

因此，您應在第二insertOne後有.then和關閉連接

代碼應該是這樣的

{ 
    db.collection('Documents').insertOne({ 
     Employeeid: 1, 
     Employee_Name: "Petro"}) 
     .then(function(db1) { 
      db1.collection('Documents').insertOne({ 
       Employeeid: 2, 
       Employee_Name: "Petra"}) 
     }).then(function(db2) { 
       db.close(); 
     }) 
    }); 

Answer 2

看評論

MongoClient.connect(url) 
    .then(function(db) { 
     // you need a return statement here 
     return db.collection('Documents').insertOne({ 
      Employeeid: 1, 
      Employee_Name: "Petro" 
     }) 
      .then(function(record) { 
       // another return statement 
       // try db instead of db1 
       return db.collection('Documents').insertOne({ 
        Employeeid: 2, 
        Employee_Name: "Petra" 
       }) 
      }) 
     .then(function() { 
      // move the close here 
      db.close(); 
     }) 

}) 
// Add an error handler 
.then(null, function(error){ 
    console.log(error) 
})