mongodb-async

Quick start

Installation

npm install mongodb-async

Usage

Syntax

Basically you can write any mongodb operation in this way:

myCollection
  .cmd(arg1, arg2, ...)
  .and(callback1)
  .and(callback2, callback3, callback4)
  .fail(errorHandler)
  .done(finishHandler);

Where cmd could be:

open, insert, save, update, remove, rename, findEach, find, findOne, findAndModify, count, distinct, createIndex, ensureIndex, getIndexes, drop, dropIndex, dropIndexes, mapReduce

Example

Let's see some real example

Require mongodb-async, there is only one entry point connect

var connect = require('mongodb-async').connect;

Connect to a server choose your db and collection

var server = connect('127.0.0.1', 27017);
var db = server.db('test_mongodb_async');
var testCollection = db.collection('test');

Yes, you can write it in this way:

var testCollection = connect('127.0.0.1', 27017).db('test_mongodb_async').collection('test');

Make some data

var doc = {x: (new Date).getTime() + ''};

Let's insert it:

var deferred = testCollection.insert(doc, {safe: true});

the onDocSaved function will be called when doc saved successfully

deferred
  .and(function onDocSaved(defer, result) {
    console.log('document saved');
    console.log(result);
    return true;
    // `return true` is equal to `defer.next(result)`, see below
  });

There're 2 ways you can make the deferred callbacks chain going to next step

• just return true, and all arguments received in current step would be passed to next step without modification.

• call defer.next({x: 'modified'}) if you want to modify data or your operation is async.

If error happens just call defer.error(yourErrorObj).

Find the inserted document:

deferred
  .and(function findDoc(outerDefer, result) {

    // Since you `return true` in previous step, the `result` passed to you here untouched.

    testCollection
      .findOne({x: doc.x})
      .and(function(innerDefer, docFound) {
        console.log('found: %s', docFound.x === result[0].x);
      })
      .fail(outerDefer.error);
      
  });
  

If you have another async operation inside, you can use .fail(outerDefer.error) to route the error to outerDefer's error handling function. Thus you can handle error in just one place

Register error handling function like this

deferred.fail(function dumpFailure(err) {
  console.error(err.stack || err);
});

Here is the above example without comments:

var connect = require('mongodb-async').connect;
var testCollection = connect('127.0.0.1', 27017).db('test_mongodb_async').collection('test');

var doc = {x: (new Date).getTime() + ''};

var deferred = testCollection.insert(doc, {safe: true})
  .and(function onDocSaved(defer, result) {
    console.log('document saved');
    console.log(result);
    return true;
  })
  .and(function findDoc(outerDefer, result) {
    testCollection
      .findOne({x: doc.x})
      .and(function(innerDefer, docFound) {
        console.log('found: %s', docFound.x === result[0].x);
      })
      .fail(outerDefer.error);
  })
  .fail(function dumpFailure(err) {
    console.error(err.stack || err);
  });