In NodeJS, how to output results from mongodb with

问题:

I'm using nodejs to query mongodb and want to output json with customized field names.

For example, original json from MongoDB maybe

    {id:1, text:"abc"}

I'd like to output it as

    {ObjectID:1, DisplayText:"abc"};

I understand MongoDB has the $project operator in its aggregate framework but not sure how to use them in NodeJS.

The mongodb nodejs packages I'm using are

    var mongo = require('mongodb');
    var monk = require('monk');
    var db = monk('server:port/mydb');

Appreciate any advice on this.

回答1:

If you are using monk as you appear to be then you can access the underlying node native driver collection type via the .col accessor on your selected collection object:

  var db = require('monk')('localhost/test')
    , collection = db.get('example');

  collection.col.aggregate(
    [
      { "$project": {
        "_id": 0,
        "ObjectID": "$_id",
        "DisplayText": "$text"
      }}
    ],
    function(err,result) {

      console.log( JSON.stringify( result, undefined, 4 ) );

    }
  );

Note that methods such as .aggregate() retrieved in this way are not wrapped in the promise object as the standard monk collection objects are. But at least this shows you how to access and use $project to re-shape your document.

回答2:

Have a look at Virtuals in Mongoose http://mongoosejs.com/docs/guide.html#virtuals

You could do something like:

someSchema.virtual('text').get(function() {
    return this.DisplayText;
}