How to execute sequence of IO task in Node.js [duplicate]

Question

I just get interest in node.js.

If everything is execute "non-blockingly", when does it flush the result to the client(browser), if I want to get result from db, post to other server, and return the result get from other server, do I need to put callback inside a callback like this?

var dbquery = db.query(function(result){
    var postToServer = otherServer.post(result.id,function(networkResult){
           render(networkResult)
    })

})

Or can be handle "more gracefully"?

I prefer to use callback's, because synch task sometimes freezes browser. — Michał Szałapski
– Michał Szałapski, Commented Aug 29, 2013 at 22:57
Note: Using or repeating tags in the title should be avoided, which is why Andy G edited to remove it. — Jonathan Lonowski
– Jonathan Lonowski, Commented Aug 29, 2013 at 23:09
"The only time you should use tags in your title is when they are organic to the conversational tone of the title", which is exactly the case here. — cababunga
– cababunga, Commented Aug 29, 2013 at 23:14
@cababunga Maybe. But, it's still redundant with the node.js tag already applied to the question. — Jonathan Lonowski
– Jonathan Lonowski, Commented Aug 29, 2013 at 23:15

Trevor Dixon · Accepted Answer · 2013-08-29 23:17:02Z

0

Use a library, something like https://github.com/kriskowal/q (promises) or https://github.com/caolan/async.

answered Aug 29, 2013 at 23:17

Trevor Dixon

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cababunga · Accepted Answer · 2013-08-29 23:15:04Z

0

This is exactly what promises are for. There are few libraries implementing them in JavaScript.

https://github.com/kriszyp/node-promise http://howtonode.org/promises

It's a bit too much to explain here, so you have to go read and look at some sample code.

Basically you code will look like this:

query_db()
.then(function (result) { return otherServer.post(result.id); })
.then(function (networkResult) { render(networkResult); });

edited Aug 29, 2013 at 23:15

answered Aug 29, 2013 at 23:09

cababunga

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