I want to drop some mongodb collections, but that's an asynchronous task. The code will be:
var mongoose = require('mongoose');
mongoose.connect('mongo://localhost/xxx');
var conn = mongoose.connection;
['aaa','bbb','ccc'].forEach(function(name){
conn.collection(name).drop(function(err) {
console.log('dropped');
});
});
console.log('all dropped');
The console displays:
all dropped
dropped
dropped
dropped
What is the simplest way to make sure all dropped
will be printed after all collections has been dropped? Any 3rd-party can be used to simplify the code.
Use Promises.
var mongoose = require('mongoose');
mongoose.connect('your MongoDB connection string');
var conn = mongoose.connection;
var promises = ['aaa', 'bbb', 'ccc'].map(function(name) {
return new Promise(function(resolve, reject) {
var collection = conn.collection(name);
collection.drop(function(err) {
if (err) { return reject(err); }
console.log('dropped ' + name);
resolve();
});
});
});
Promise.all(promises)
.then(function() { console.log('all dropped)'); })
.catch(console.error);
This drops each collection, printing “dropped” after each one, and then prints “all dropped” when complete. If an error occurs, it is displayed to stderr
.
Use Q promises or Bluebird promises.
With Q:
var Q = require('q');
var mongoose = require('mongoose');
mongoose.connect('your MongoDB connection string');
var conn = mongoose.connection;
var promises = ['aaa','bbb','ccc'].map(function(name){
var collection = conn.collection(name);
return Q.ninvoke(collection, 'drop')
.then(function() { console.log('dropped ' + name); });
});
Q.all(promises)
.then(function() { console.log('all dropped'); })
.fail(console.error);
With Bluebird:
var Promise = require('bluebird');
var mongoose = Promise.promisifyAll(require('mongoose'));
mongoose.connect('your MongoDB connection string');
var conn = mongoose.connection;
var promises = ['aaa', 'bbb', 'ccc'].map(function(name) {
return conn.collection(name).dropAsync().then(function() {
console.log('dropped ' + name);
});
});
Promise.all(promises)
.then(function() { console.log('all dropped'); })
.error(console.error);