小编Khu*_*hid的帖子

我正在学习使用mongdb gridfs和nodejs驱动程序.我第一步陷入困境.

var MongoClient = require('mongodb').MongoClient;
var Grid = require("mongodb").Grid;

MongoClient.connect("mongodb://localhost:27017/kkdb", function(err, db) {
   if(err) return console.log("error in connection:>>>>>>>>>>>>>>> ", err); 

   var grid = new Grid(db, 'fs');
   var buffer = new Buffer("Hello world");

   grid.put(buffer, {metadata:{category:'text'}, content_type: 'text'}, function(err, fileInfo) {
       if(!err) {
           console.log("Finished writing file to Mongo");
       }
   });
});

当我运行此代码时,它显示错误:TypeError: Grid is not a constructor

将mongodb与NodeJS驱动程序一起使用

我有2个收藏品.一个用于部门,另一个用于学生.

Deparmtent的示例数据.

{ 
 "_id" : ObjectId("5a24d20590d3d12155f3094e"), "name" : "CSE", "hod" : 
 "abc", 
 "students" : [ 
  ObjectId("5a2129172c3e542acb78c1f5"),
  ObjectId("5a2129172c3e542acb78c1f7"), 
  ObjectId("5a2129172c3e542acb78c1f9"), 
  ObjectId("5a2129172c3e542acb78c1fb")
 ]
}

{
 "_id" : ObjectId("5a24d20590d3d12155f3094f"), 
 "name" : "IT", 
 "hod" : "xyz", , 
 "students" : [ 
  ObjectId("5a2129172c3e542acb78c1f6"),
  ObjectId("5a2129172c3e542acb78c1f8"), 
  ObjectId("5a2129172c3e542acb78c1fa"),
  ObjectId("5a2129172c3e542acb78c1fc") 
 ] 
}

和学生的样本数据

{
    "_id" : ObjectId("5a2129172c3e542acb78c1f4"),
    "rollNumber" : 11,
    "name" : "Thor",
    "branch" : ObjectId("5a24d20590d3d12155f3094e"),
}

这是查询:

aggregate([
   {$lookup: 
     { from: "students", 
       localField: "_id", 
       foreignField: "branch", as: "studentData"
     }
   }
])

输出查询

[ 
  { _id: 5a24d20590d3d12155f3094e,
    name: 'CSE',
    hod: …