Synchronous DB requests Node JS ORM

Question

I need to populate array with values from DB and only then return it, so how can i make this Synchronous

 var convs = Array; User.find({token: token}).first(function(err, user) { ConversationData.find({user_id: 1}).each().forEach(function(convData) { ConversationData.count({conversation_id: convData.conversation_id}, function(err, count) { if(count == 2) { var user2; console.log(convData.user_id); ConversationData.find({user_id: 2, conversation_id: convData.conversation_id}).first(function(err, usr) { user2 = usr; }); Message.find({conversation: convData.conversation_id}, [ "createdAt", "Z" ]).first(function(err, msg){ convs[convData.id].conversation = convData.id; convs[convData.id].lastMessage = msg.content; convs[convData.id].lastMessageDate = msg.createdAt; convs[convData.id].title = user2.name + " " + user2.name; convs[convData.id].avatar = user2.avatar; }); } else { console.log('COUNT = ' + count); } }); }); console.log(convs);

node.js doesn't work like that. If you want something that looks synchronous, use generators, a language that compiles to async javascript, or something similar. One of node's big selling points is that i/o is asynchronous. — mscdex
– mscdex, Commented Apr 3, 2016 at 19:38

pkm · Accepted Answer · 2016-04-03 19:53:13Z

What is the context for what you are trying to do? You cannot make async operations synchronous. Instead you must call another function to tell your program that the async operation has completed.

For example, if you are responding to a client request, you can send the response from within your callback once you have the complete result, e.g. response.send(result); Else, you might call a done() function or some similar function to pass along the result.

To represent the eventual result in your code, and also free yourself from nested callbacks, look into replacing your callback functions with Promises. e.g.

return User.find({token: token}).then(function(userData){ return Conversation.find({id: userData.id}); }).then(function(conversationData){ return Message.find({conv_id: conversationData.id}); //or response.send(conversationData) etc })

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