node.js - Render page in express after for loop completes -

i have run mongoose query repeatedly within loop , once completes, want render page in express. sample code given below. since mongoose runs asynchronously, how can make 'commands/new' page render once 'commands' array has been populated within loop?

... ... var commands = []; (var index=0; index<ids.length; index++) {     mongoose.model('command').find({_id : ids[index]}, function (err, command){         // biz logic 'command' object         // , add 'commands' array         commands[index] = command;     }); }  res.render('commands/new', {     commands : commands }); ... ... 

your basic for loop here not respect callback completion of asynchronous methods calling before executing each iteration. use instead. node async library fits bill here, , in fact better methods of array iteration:

var commands = [];  async.each(ids,function(id,callback) {     mongoose.model("command").findbyid(id,function(err,command) {         if (command)              commands.push(command);         callback(err);     }); },function(err) {    // code run on completion or err }) 

and therefore async.each or possibly variant async.eachlimit run limited number of parallel tasks set better loop iteration control methods here.

nb .findbyid() method of mongoose helps shorten coding here.